Transmission apparatus and method for transmission of data in a multi-carrier broadcast system

ABSTRACT

A transmission apparatus and method, respectively, mapping payload data of mapping input data streams onto a mapping output data stream having a channel bandwidth for transmission in a multi-carrier broadcast system. To enable selection of robustness for transmission of data, the apparatus includes a frame forming mechanism mapping data blocks of at least two mapping input data streams onto frames of the mapping output data stream covering the channel bandwidth, each frame including a payload portion, the payload portion including plural data symbols and being segmented into data segments each covering a bandwidth portion of the channel bandwidth. The frame forming mechanism is configured to map the data blocks of the at least two mapping input data streams onto data symbols of the payload portion and includes a MIMO mode selector selecting a MIMO mode of the data blocks per data segment and/or per mapping input data stream.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/579,727 filed on Sep. 17, 2012, which claims the benefit of theearlier filing date of 10154717.2 filed in the European Patent Office onFeb. 25, 2010 and 10192096.5 filed in the European Patent Office on Nov.22, 2010 and is a national stage application of the internationalapplication PCT/EP 2011/052222 filed on Feb. 15, 2011, the entirecontents of each of which applications is incorporated herein byreference.

FIELD OF INVENTION

The present invention relates to a transmission apparatus comprising anapparatus for mapping payload data of mapping input data streams onto amapping output data stream having a channel bandwidth for transmissionin a multi-carrier broadcast system. Further, the present inventionrelates to a receiving apparatus for receiving data within amulti-carrier broadcast system. Still further, the present inventionrelates to corresponding methods and a non-transitory computer-readablerecording medium.

The present invention relates, for instance, to the field of DigitalVideo Broadcasting (DVB) utilizing Orthogonal Frequency DivisionMultiplexing (OFDM). Further, the present invention can generally beapplied in other broadcast systems, such as DAB (Digital AudioBroadcasting), DRM (Digital Radio Mondial), MediaFlo, ISDB systems or afuture ATSC system. However, it should be noted that the invention isnot limited to the use of OFDM, but can generally be applied in allmulti-carrier broadcast systems and their components.

BACKGROUND OF THE INVENTION

The transmission parameters of known broadcast systems, such as thebroadcast systems in accordance with the DVB-T2 standard (secondgeneration digital terrestrial television broadcast systems standard asdefined in ETSI EN 302 755 V1.1.1 (2009-09) “Digital Video Broadcasting(DVB); Framing structure Channel Coding and Modulation for a SecondGeneration Digital Terrestrial Television Broadcast system (DVB-T2)”),are generally optimized for fixed reception with stationary receivers,e.g. with roof-top antennas, for which low power consumption is not amain issue. Further, according to this standard a fixed channelbandwidth is generally used. In future broadcast systems, such as theupcoming DVB-NGH (DVB Next Generation Handheld; in the following alsoreferred to as NGH) standard, a mobile receiver (which is the main focusof this upcoming standard) shall support a variety of different channelbandwidths, e.g. ranging from 1.7 MHz to 20 MHz wide channels. Further,such a mobile receiver has to account for specific needs of mobile andhandheld reception, i.e. low power consumption and high robustness.

SUMMARY OF INVENTION

It is an object of the present invention to provide a transmissionapparatus and method comprising an apparatus and a corresponding method,respectively, for mapping payload data of mapping input data streamsonto a mapping output data stream having a channel bandwidth fortransmission in a multi-carrier broadcast system, which selectivelyprovide a high robustness of the data transmission and which enable theuse of narrow-band receivers having a low power consumption. It is afurther object of the present invention to provide a correspondingreceiving apparatus and method and a non-transitory computer-readablerecording medium.

According to an aspect of the present invention there is provided atransmission apparatus for transmitting data within a multi-carrierbroadcast system, comprising a transmitter unit for transmitting saidmapping output data stream, an apparatus for mapping payload data ofmapping input data streams onto a mapping output data stream having achannel bandwidth for transmission in a multi-carrier broadcast system,and wherein said apparatus for mapping comprises

-   -   a data input for receiving said at least two mapping input data        streams each being subdivided into data blocks carrying payload        data,    -   a frame forming means for mapping the data blocks of said at        least two mapping input data streams onto frames of said mapping        output data stream covering said channel bandwidth, each frame        comprising a payload portion, said payload portion comprising a        plurality of data symbols and being segmented into data segments        each covering a bandwidth portion of said channel bandwidth,        wherein the frame forming means is adapted for mapping the data        blocks of said at least two mapping input data streams onto the        data symbols of said payload portion and comprises a MIMO mode        selection means for selecting the MIMO mode of the data blocks        per data segment and/or per mapping input data stream, and    -   a data output for outputting said mapping output data stream.

According to a further aspect of the present invention there is provideda receiving apparatus for transmitting data within a multi-carrierbroadcast system.

According to further aspects of the present invention there is provideda transmission method, a receiving method and a non-transitorycomputer-readable recording medium that stores therein a computerprogram product, which, when executed by a processor, causes the methoddisclosed herein to be performed.

Preferred embodiments of the invention are defined in the dependentclaims. It shall be understood that the claimed apparatus and methodsand the claimed medium have similar and/or identical preferredembodiments as the claimed transmission apparatus and as defined in thedependent claims.

One of the ideas of the present invention is to apply the concept ofband segmentation in the frames in order to enable the use ofnarrow-band receivers for receiving and processing the frames. Such asegmentation of the payload portion (which carries the actual payloaddata) of the frames, according to which the payload portion is segmentedinto (two or more) data segments each covering a bandwidth portion ofthe total channel bandwidth, the power consumption of the usednarrow-band receiver can be kept low. Additionally, one fixed receivertuner bandwidth is sufficient for the reception of all availabletransmission bandwidths.

The frame structure applied for the frames thus uses the bandsegmentation concept as, for instance, described in the DVB-C2 standard(DVB BlueBook A138 “Digital Video Broadcasting (DVB); frame structurechannel coding and modulation for a second generation digitaltransmission system for cable systems (DVB-C2)”) according to which thetotal channel bandwidth is divided into data slices (generally referredto herein as “data segments”). Further, quite similar as described inthe DVB-C2 standard, the frames may in an embodiment comprise a preambleportion in addition to the payload portion, wherein the preamble portioncomprises at least one preamble symbol carrying at least one preamblesignalling block including signalling data. The data segments of thepayload portion may have flexible bandwidths and are generally notaligned to a frequency raster. All data of a mapping input data streammay be transmitted within one data segment, but this is not an essentialrequirement as will be explained below. Further, while the preamblesignalling blocks are aligned to a frequency raster, the data segmentstypically do not follow any channel raster and can even have flexiblebandwidths. Data segments may also be combined in frequency direction toan overall broader data pipe having a broader bandwidth, and may alsocontain data of more than one mapping input data stream.

Further, the concept of absolute OFDM may be applied for the framestructure of the frames, according to which all OFDM subcarriers areseen relative to the absolute frequency 0 MHz instead of a signal centerfrequency. Reason for the application of absolute OFDM and unique pilotpattern across the medium spectrum, as applied in DVB-C2, is to avoid inthe preamble symbols repeating OFDM subcarrier allocations in thefrequency domain that result in an increased PAPR (Peak to Average PowerRatio). Furthermore, the recognition of signals provided for particularreceivers (e.g. mobile receivers, for instance according to the upcomingDVB-NGH standard) during initial acquisition gets faster and morereliable with the help of the frequency specific pilot patterns.

Another idea of the present invention is to provide the ability to themapping apparatus to select the MIMO mode of the data blocks (alsoreferred to as “bursts” or “data patterns”) per data segment (alsoreferred to as “data slice”) and/or per mapping input data stream (alsoreferred to as “PLP” or “physical layer pipe”), i.e. for each particulardata segment and/or for each particular mapping input data stream it ispossible to determine the MIMO mode of the data blocks so that the datablocks are transmitted by use of a respective antenna configuration ofthe transmitter. Selection of the MEMO mode here means that it ispossible during the mapping of the data blocks onto the frames to selectby which antenna configuration the data blocks of a particular mappinginput data stream (which may be mapped onto a single or several datasegments) and/or the data blocks that shall be mapped onto a datasegment (which may belong to a single or several mapping input datastreams) shall be transmitted. Hence, for instance, the service providerof a particular service may determine that his service (i.e. his mappinginput data stream shall be transmitted with a high robustness comparedto another service that shall be transmitted with a lower robustness,but with a higher throughput rate. The antenna configuration (i.e. theMIMO mode) used for transmitting the data blocks of said services maythus be selected accordingly.

Generally, all possible MIMO modes are available for selection, i.e. theterm MIMO mode shall not be construed as being limited to selecting aMIMO (Multiple Input Multiple Output) antenna configuration, using atleast two antennas for transmission in the transmitter and at least twoantennas for reception in the receiver. In contrast, other modes and,thus, other antenna configurations shall also be available forselection, and the term MIMO mode selection shall thus be understoodbroadly in this broad sense. In an embodiment, the MIMO mode selectionmeans is adapted for selecting one of a SISO (Single Input SingleOutput) scheme, MISO (Multiple Input Single Output) scheme or MIMOscheme, which represent the most common schemes, i.e. the MEMO modeavailable for selection can be MIMO, MISO or SISO scheme (often alsocalled “mode” or “antenna configuration”) in this embodiment. In theselection of the used MIMO mode a trade-off can be made between highrobustness but increased mapping and processing capacity versus lowerrobustness and lower mapping and processing capacity. As an example, acertain service (e.g. news broadcast) can be transmitted using MISOscheme, such that even fast moving receivers (e.g. in cars or trains)can receive this service, while at a later time, the next service mighttarget only stationary or portable receivers and thus uses a MIMOscheme, which results in a higher data rate but requires a higherreception quality. Finally, in the given example, a low bit rate radioservice can be transmitted using SISO such that decoding becomes simple.Furthermore, SISO offers the advantage that the number of pilots forchannel estimation can be reduced compared to MISO or MIMO transmission.

It should be noted here that there are generally two different basicantenna arrangements available in MIMO and MISO schemes. In one antennaarrangement two or more transmission antennas are arranged spatiallydistinct (so-called distributed MIMO/MISO). In another antennaarrangement the two or more antennas are located close together, but thetransmitted signals are differently polarized (so-called co-locatedMIMO/MISO).

In an embodiment said MIMO mode selection means is adapted for changingthe MIMO mode from frame to frame or from a group of frames to a nextgroup of frames. Hence, some flexibility in the MIMO mode selection isprovided, which allows e.g. targeting different receiver types, ortransmitting data in MIMO scheme only in a specific part of a mappingoutput data stream, while data in SISO scheme is transmitted in theremaining parts. Further, this embodiment can be used to change the MIMOmode for a new service that is mapped onto a new frame or a new group offrames.

Further, in an embodiment said MIMO mode selection means is adapted formapping the data blocks onto the data symbols of the data segments suchthat the MIMO mode changes from data symbol to data symbol or from agroup of data symbols to a next group of data symbols, which allows e.g.targeting different receiver types, or transmitting data in MIMO modeonly in a specific part of a mapping output data stream, while data inSISO scheme is transmitted in the remaining parts. Furthermore, thisscheme allows e.g. for the application of scalable video coding, wherethe robust layer is transmitted in SISO scheme, while the enhancementlayer is transmitted in MIMO scheme. Thus, decoding of the robust layeris also possible in channel conditions where MIMO decoding fails (e.g.correlated channels).

In another aspect of the present invention an apparatus for mappingpayload data of mapping input data streams onto a mapping output datastream having a channel bandwidth for transmission in a multi-carrierbroadcast system is provided, said apparatus comprising

-   -   a data input for receiving said at least two mapping input data        streams each being subdivided into data blocks carrying payload        data,    -   a frame forming means for mapping the data blocks of said at        least two mapping input data streams onto frames of said mapping        output data stream covering said channel bandwidth, each frame        comprising a payload portion, said payload portion comprising a        plurality of data symbols and being segmented into data segments        each covering a bandwidth portion of said channel bandwidth,        wherein the frame forming means is adapted for mapping the data        blocks of said at least two mapping input data streams onto the        data symbols of said payload portion and comprises a pilot,        pattern selection means for selecting the pilot pattern per data        segment and/or per mapping input data stream, and    -   a data output for outputting said mapping output data stream.

This aspect provides another option for selecting the robustness(especially for reliable channel estimation at the receiver) of datablocks of data segments and/or mapping input data streams. This optioncan be provided as an alternative or in addition to the MIMO modeselection means of the MIMO mode per data segment and/or per mappinginput data stream, but can also be provided in addition thereto.

In particular, in a further embodiment said pilot pattern selectionmeans is adapted for increasing the pilot density in time and/orfrequency direction, in particular depending on the number oftransmission antennas and/or the desired robustness level, since byselecting a higher pilot density a higher robustness can be achieved.

Preferably, said pilot pattern selection means is adapted for providingedge pilots for one or more neighbouring data segments, said edge pilotsfitting with the pilot patterns of said one or more neighbouring datasegments. Said fitting can, for instance, be achieved by selecting edgepilots such that they are a multiple of the pilot patterns of the twoneighbouring data segments, between which the (common) edge pilots areprovided, or of a single neighbouring data segment (if the edge pilotsare provided at the beginning or end in frequency direction of a datasymbol). Hence, both segments can employ these edge pilots, and nofrequency gap is required between data segments. Furthermore, therequired pilot overhead is limited to a minimum, as both data segmentsemploy the same (common) edge pilots.

Preferably, said pilot pattern selection means is adapted for changingthe pilot pattern from frame to frame or from a group of frames to anext group of frames. Hence, some flexibility in the pilot patternselection is provided. If e.g. a SISO signal is transmitted in a frame,only the SISO pilots have to be transmitted, which require significantlyless overhead compared to MIMO pilots. Furthermore, also the density ofthe pilots can be adjusted to different scenarios, e.g. differentreceiver velocities. As an example, a certain service (e.g. newsbroadcast) can be transmitted with a high pilot density, such that evenfast moving receivers (e.g. in cars or trains) can receive this service,while at a later time, the next service might target only stationary orportable receivers and thus uses a smaller pilot density, which resultsin a higher data rate.

In an embodiment, said frame forming means further comprises a bufferunit per mapping input data stream for storing preprocessed data blocksof an associated mapping input data stream therein until they are mappedonto a frame, wherein said frame forming means, in particular ascheduler thereof, is adapted for retrieving data blocks from a bufferand mapping them onto a data segment of a frame, if sufficient datablocks are stored therein for filling a complete data symbol. Thisprovides an efficient way of filling the data segments of the frameswith the data blocks.

In an embodiment said frame forming means is adapted for mapping thedata blocks of said at least two mapping input data streams onto thedata segments of a frame such that into a data segment only data blockshaving the same MIMO mode and/or pilot pattern are mapped. Thisfacilitates the transmission of the data and the signalling to thereceiver since within a data segment only a single MIMO mode and/orpilot pattern is applied so that per data segment only one single pieceof signalling information must be provided to the receiver.

In a preferred embodiment said frame forming means is adapted formapping signalling information into said frame, said signallinginformation including MIMO mode information indicating the selected MIMOmode of the data blocks per data segment and/or per mapping input datastream and/or pilot pattern information indicating the selected pilotpattern per data segment and/or per mapping input data stream. Thereceiver thus easily knows which MIMO mode and/or pilot pattern isapplied and can thus correctly receive and decode the received datablocks. Further, this enables the receiver to switch off particularreceiving antennas or complete receiving paths, if the signallinginformation signals that only a single receiving antenna (and alsofurther elements, like tuner, demodulator, etc.) is generally requiredas is, for instance, the case in SISO or MISO scheme. In this way,processing capacity and power can be significantly saved in the receiverin certain MIMO modes. Alternatively, mechanisms like maximum ratiocombining can be used to increase the decoding probability.

To enable the receiver to obtain all the required signalling informationfor receiving all the data blocks of the desired data stream, which isparticular important if the data blocks are multiplexed in time andfrequency direction and/or if they are irregularly mapped onto theframe, various embodiments exist for informing the receiversaccordingly.

Optionally, said frame forming means is adapted for including saidsignalling information into one or more preamble signalling blocksmapped onto preamble symbols of a preamble portion of said frames, intoone or more payload portion signalling blocks mapped onto data symbolsof said payload portion or in-band into one or more data blocks mappedonto data symbols of said payload portion. Hence, according to oneembodiment all the required signalling information could be put into thepreamble signalling blocks. This, however, would require quite largepreamble signalling blocks forcing the receiver to receive and processquite a lot of information which is not all required if only oneparticular data stream shall be received, i.e. the signalling data forthe other data streams is not required and thus superfluous in suchsituation. This would also lead to time delays of the processing of theactual data to be received. On the other hand, one advantage would bethat zapping could be faster, as all signalling information is alreadyknown.

Hence, according to a preferred embodiment the at least one preamblesignalling block comprises only high level, rough signalling informationabout the mapping of the data blocks onto the data segments of theframes and the frame forming means is adapted for mapping payloadportion signalling blocks comprising low level, more detailed signallinginformation about the mapping of the data blocks onto the data symbolsof the frames. According to this embodiment the main information forenabling the receiver to receive and process a particular data stream isprovided in said payload portion signalling blocks, which can generallybe regarded and processed by the frame forming means as an own mappinginput stream and which can thus be mapped onto the frames in the sameway as the other mapping input data streams. The information containedin the payload portion signalling blocks thus, for instance, containsthe information about the code rate, modulation, number of subsequentlyarranged FEC-frames, the number of data blocks within a frame and theinformation about the location of the data blocks within the frame. Thisinformation for a particular mapping input data stream can either be putinto one payload portion signalling block and can be cyclicallyrepeated, or it can be divided into several pieces of informationdistributed over multiple payload portion signalling blocks. The use ofsuch payload portion signalling blocks mapped onto the payload portionprovides the additional advantage that a time diversity of said payloadportion signalling blocks can be provided resulting in a higherrobustness of the signalling information. This signalling is similar tothe L1 signalling as done according to the DVB-T2 standard, wherebyfurther or other parameters are included as needed.

To enable the receiver to find at least one payload portion signallingblock the at least one preamble signalling block preferably comprises atleast one pointer to a payload portion signalling block. Hence, thereceiver first obtains said pointer from the preamble signalling blockand then uses the pointer to find the payload portion signalling blockby use of said pointer, obtains the signalling information containedtherein which then enables the receiver to find the data blocks of thedesired data stream. Hence, the preamble signalling blocks can be shortsince basically pointers and only some other general signallinginformation needs to be provided therein.

The provision and use of a pointer in the preamble portion is, however,not mandatory. For instance, according to an alternative embodiment, theposition of the payload portion signalling block(s) is predefined andknown a priori in the receiver, e.g. predefined in a standard orpre-programmed in the transmitter and all receivers.

In an even more elaborate embodiment it is proposed that the frameforming means is adapted for mapping in-band signalling informationcomprising low level, more detailed signalling information about themapping of data blocks of a particular mapping input data stream ontothe data segments of the frames into one or more of said data symbols,in particular into all data symbols carrying data blocks of saidparticular mapping input data stream. Hence, the concept of in-bandsignalling may additionally be used in the frames. Said in-bandsignalling information may, for instance comprise the information wherethe next data block of the same mapping input data stream can be found.Thus, all this signalling information needs not to be decoded from thepreamble signalling blocks and/or the payload portion signalling blocks,which thus only need to enable the receiver to find the first datablock. If the receiver has decoded said data blocks it can also read thein-band signalling information contained therein enabling the receiverto find the next data block. This concept is preferably provided in thedata blocks of all mapping input data streams mapped onto the frames.

According to still another embodiment the frame forming means is adaptedfor mapping payload portion signalling blocks onto data symbols of oneor more particular frames, wherein signalling information, in particularpointers, about the mapping of the data blocks onto the data symbols ofone or more subsequent frames, in particular the next superframe, isincluded into said payload portion signalling blocks. Hence, in a frameall the required signalling information can be found by the receiver inthe payload portion signalling blocks that are required to find all datablocks mapped onto one or more subsequent frames, i.e. a group of framesor the frames of a superframe. This requires for the receiver a bit moretime for obtaining all the signalling information, but allows instantzapping of the receiver between all data streams without any waitingtime for first obtaining the required signalling information. In otherwords, the signalling information is obtained in advance and withoutknowing if and which parts thereof all are really required by thereceiver.

According to a further refinement the frame forming means is adapted forincluding offset signalling information indicating changes of themapping of the data blocks between said one or more particular framesand said one or more subsequent frames into in-band signallinginformation of a data block or into one or more payload portionsignalling blocks mapped onto data symbols of said one or moreparticular frames. Hence, at the end of a frame said offset signallinginformation can be mapped as in-band signalling information into one ormore data blocks. Alternatively, said offset signalling information canbe mapped into one or more payload portion signalling blocks. Saidoffset signalling information indicates how the signalling informationchanges from this (group(s) of) frame(s) to the next (group(s) of)frame(s) (or any other subsequent frame(s)) so that in the next (orsubsequent) (group(s) of) frame(s) all the signalling information mustnot necessarily be mapped into payload portion signalling blocks or mustat least not be obtained by the receiver. In other words, mainly someoffset information is mapped into the frames to save mapping space andtime (in the receiver, which can be continuously tuned to the desireddata stream and needs not access the payload portion signalling blocksagain).

In another embodiment said frame forming means further comprises one ormore mapping units per transmission path of a transmitter into whichsaid apparatus is included, wherein said one or more mapping units areadapted for individually mapping substantially the same data blocks ofthe provided mapping input data stream onto individual frames. Hence, inthe various MIMO modes the required mapping can be applied by thevarious frame forming units. For instance, in SISO scheme the data caneither be transmitted by only a single antenna, but can also betransmitted—in identical form—by two or more antennas. On the receiverside, for instance, in SISO scheme the data can either be received byonly a single antenna, but can also be received—in identical form—by twoor more antennas (single input, multiple output, SIMO scheme). Also inMIMO all reception paths are generally active. In MISO scheme the dataof one transmission path can be subjected to an additional coding, e.g.Alamouti coding as defined in the DVB-T2 standard, whereas the data onthe other transmission path are not further coded. Therefore, in anotherembodiment at least one mapping unit comprises encoding means forencoding the data blocks provided to said at least one mapping unit.

Still further, in an embodiment said frame forming means is adapted formapping the data blocks of a mapping input data stream onto a frame suchthat they are spread in time and frequency over various data symbols andvarious data segments of said frame. Hence, according to thisembodiment, the data blocks of a mapping input data stream are not onlymapped onto a single data segment or onto two or more data segments, butare mapped onto various, e.g. all, data segments of the frame. In otherwords, time and frequency multiplexing is applied to the data blocks ofa mapping input data stream providing time and frequency diversityincreasing the overall robustness against different kinds ofdisturbances that might appear on the transmission channel, which isparticularly important when considering the reception by mobilereceivers. In addition, the data contained in the data blocks may beinterleaved in advance, and generally the data are also protected by aforward error correction code, such as an LDPC code.

According to a preferred embodiment the frame forming means is adaptedfor mapping the data blocks of a mapping input data stream onto a framesuch that they are mapped onto a single data segment or onto two ormore, in particular neighbouring, data segments of said frame. Hence, asmentioned above, data segments can be combined to obtain a broader “datasegment”, which is also referred to as a “data pipe”. The same conceptof a segmented payload portion of the frames can be used, even ifmapping input data streams having a higher data density shall be mappedonto a frame. According to a more general scenario the data blocks of aparticular mapping input data stream are mapped onto two or more datasegments, which are not neighbouring in frequency direction. In allthese embodiments the receiver needs to have a broader bandwidth.

According to further embodiments the frame forming means is adapted forselecting the bandwidth of said data segments of the payload portion ofthe frames. Hence, the bandwidth may be variable and selected as needed,for instance according to the amount of data of a mapping input datastream to be mapped on the frames. Alternatively, as proposed accordingto another embodiment, the data segments of the payload portion of theframes may have a predetermined bandwidth, in particular an equalbandwidth, in all frames. The latter embodiment requires less signallingsince the receivers can be appropriately adapted in advance forreception of the known predetermined bandwidth.

Further, according to an embodiment the frame forming means is adaptedfor mapping the data blocks of a mapping input data stream onto a framesuch that at each time at most one data symbol comprises a data block ofa particular mapping input data stream. Hence, according to thisembodiment a further improvement of time diversity is obtained furtherincreasing robustness and a narrow-band receiver can detect thisservice.

Further, in an embodiment the frame forming means is adapted for mappingthe data blocks of a mapping input data stream onto a frame such thatthe data blocks are irregularly mapped onto data symbols of the frame.This embodiment also contributes to an increase of the robustness, inparticular against regular disturbances. Irregular particularly meansthat there is no predefined or any regular mapping, e.g. that isperiodic in time and/or frequency direction, of the data blocks of amapping input data stream onto the data symbols both in time andfrequency direction, e.g. a sequential sorted arrangement that could besusceptible to periodic disturbances.

Still further, in an embodiment the frame forming means is adapted formapping the data blocks of a mapping input data stream onto a frame suchthat between data symbols carrying a data block of a particular mappinginput data stream there is one or more data symbol in time directioncarrying no data block of the same particular mapping input data stream.This embodiment also contributes to an increase of the robustness, butprovides the further advantage that the receiver may fall into sleepmode and, thus, save power in between data symbols carrying data blocksof the mapping input data stream that shall be received, i.e. datasymbols carrying no data blocks of the mapping input data stream thatshall be received are not received or at least not completely processedin the receiver. Further, this provides the ability to the receiver toestimate the channel prior of fully waking up.

According to a preferred embodiment the frame forming means is adaptedfor segmenting the preamble portion of the frames into preamble segmentsall having an identical fixed bandwidth. This solution corresponds, asmentioned above, to the segmentation of the preamble portion as, forinstance, described in the DVB-C2 standard according to which L1 blocksare provided in the preamble portion. In an embodiment the bandwidth ofthe preamble segments is equal to or larger than the bandwidth of thedata segments. Alternatively, the bandwidth can also be smaller, e.g. ifless signalling information must be put into the preamble segments.Generally, the bandwidth of both the preamble segments and the datasegments is smaller than the receiver bandwidth.

In a further embodiment the frame forming means is adapted for mappingsubstantially the same signalling data onto all preamble segments of thepreamble portion of a frame. Thus, the same signalling data iscontinuously provided in the preamble signalling blocks (which mightslightly differ from each other, e.g. have different pilots and/or aredifferently scrambled), but enable a receiver always to be able toreceive signalling data, irrespective to which data segment it is tuned.Hence, even if the tuning position of a receiver is not aligned to thefrequency raster of the preamble segments, the receiver is able toobtain the signalling data by sorting the signalling data out of twoadjacent preamble signalling blocks since the signalling data ispreferably cyclically repeated within the preamble portion.

In an embodiment the mapping apparatus further comprises

-   -   a second frame forming means for mapping the data blocks of a        first group of received mapping input data streams onto first        frames having a first frame structure covering said channel        bandwidth for use by receivers of a first type, wherein said        frame forming means is adapted for mapping the data blocks of a        second group of received mapping input data streams onto second        frames having a second frame structure covering said channel        bandwidth for use by receivers of a second type, which second        frame structure is different from the first frame structure, and    -   a stream forming means for forming said mapping output data        stream by alternately arranging one or more first and one or        more second frames.

This embodiment is based on the idea to construct the mapping outputdata stream such that it comprises two different types of frames, eachhaving its own frame structure. These two types of frames arealternately arranged in the mapping output data stream such thatalternately one or more second frames follow one or more first framesand so on as, for instance, defined in the superframe structureaccording to the DVB-T2 standard, according to which T2-frames and FEFframes (Future Extension Frames) are alternately arranged. The firstframes are designed for reception by a first type of receiver, e.g. astationary receiver such as a DVB-T2 receiver, while the second frames(i.e. the “frames” as explained above in detail) are designed forreception by a second type of receiver, e.g. a mobile receiver such as aDVB-NGH receiver.

The frame structure applied for the first frames may, as proposedaccording to a preferred embodiment, be the frame structure as describedin the DVB-T2 standard for the T2-frames, and the second frames may bethe FEF frames as described in the DVB-T2 standard. Both frames may thusbe arranged alternately to obtain a superframe structure as generallydescribed in the DVB-T2 standard. Further, both frames may carry datafrom the same mapping input data streams but with a different robustnesslevel and different data throughput (i.e. different data density) ifdesigned for reception by different kinds of receivers. For instance,the first frames may carry the data with a high density for reception bystationary receivers, while the second frames may carry the same datawith low density for reception by mobile receivers. In otherembodiments, however, the two different types of frames may carry datafrom different (or only partly the same) mapping input data streams, forinstance if different services or data shall be provided to thedifferent kinds of receivers.

As mentioned above, the first frames may be formed in accordance withthe DVB-T2 standard and the second frames may be formed in accordancewith the DVB-C2 standard. The mapping input data streams can thus beregarded as physical layer pipes, wherein each physical layer pipe issegmented into subslices or bursts representing the above-mentioned datablocks, which carry error correction code encoded, interleaved data. Theinvention, however, is not limited to such embodiments and applications,but other frame structures and other kinds of mapping input data streamsin other applications (using other standards or no particular standard)may be used as well.

It has been found that generally for changing from the transmission ofdata in a SISO scheme (requiring only a single transmission antenna) tothe transmission of data in a MIMO or MISO scheme (requiring at leasttwo transmission antennas) in time domain it is needed to quickly switchthe one or more further transmission antennas on and off Due to the highpower used for transmission in the field of broadcasting, othersolutions are needed.

For solving this problem, in an embodiment the transmission apparatus asproposed according to the present invention is adapted for transmittinga mapping output data stream in which the MIMO mode of the data blocksis selected per data segment, wherein said transmitter unit comprises atleast two transmission antennas, wherein a first transmission antenna isadapted for transmission of data blocks mapped onto data segments in anyMIMO mode and wherein the further transmission antennas are adapted fortransmission of data blocks mapped onto data segments in the MISO schemeor MIMO scheme. Hence, no quick on and off switching of transmissionantennas in time domain is required, but the transmission antennas aregenerally switched on all the time but are generally using differentnumbers of subcarriers.

Preferably, said further transmission antennas are adapted to usedifferently polarized subcarriers than the first antenna. For instance,in an embodiment of a transmission apparatus a first transmissionantenna uses vertically polarized subcarriers, while a secondtransmission antenna uses horizontally polarized subcarriers.Alternatively, the various antennas may use different circularpolarizations. In still another alternative embodiment of a transmissionapparatus the various transmission antennas deploy spatial diversity,i.e. they may be located at considerable distances from each other, i.e.not at substantially the same place, but rather separated by about 5-10times the wavelength, and may then use the same polarization. Further,combinations of all schemes are also possible (spatially separated and(circular) polarized, . . . )

Advantageously, said frame forming means is adapted for generating OFDMsymbols for transmission by said further transmission antennas over thecomplete channel bandwidth. Thus, a single wide-band OFDM symbol is usedin this embodiment by said further transmission antennas.

In this embodiment said frame forming means is preferably adapted forsetting subcarriers used by said further transmission antennas to zeroin bandwidth portions of said channel bandwidth covered by data segmentsonto which data blocks are mapped in the SISO scheme. Thus, only asingle OFDM symbol has to be generated and synchronization in time andfrequency is eased.

Alternatively, said frame forming means is adapted for generating OFDMsymbols for transmission by said further transmission antennas, an OFDMsymbol comprising two or more partial OFDM symbols, each partial OFDMsymbol comprising only directly adjacent, non-zero subcarriers. Thus,two or more narrow-band OFDM symbols are used in this embodiment by saidfurther transmission antennas. This approach yields smaller PAPR valuesfor each partial OFDM and further allows the construction of verybroadband OFDM signals of smaller building blocks. However, the partialOFDM signals have to be shifted (mixed) to the corresponding datasegments with perfect time and frequency synchronization.

Further, in an embodiment said further transmission antennas are adaptedfor each substantially using the same total transmission power as thefirst transmission antenna and for each substantially equallydistributing the total transmission power to the non-zero subcarriers.This ensures that each transmission antenna can transmit with the sametotal power which is generally desired in case of several transmissionantennas in a MIMO or MISO transmission system. This helps to avoidpower imbalances at the receiver for the detection of the differenttransmission antennas prior to OFDM demodulation, thereby achieving thebest possible average SNR values for the different reception antennas.This provides an advantage, since many MIMO schemes suffer from powerimbalances, e.g., spatial multiplexing MIMO.

Preferably, said transmission antennas are adapted for eachsubstantially using the same transmission power per non-zero subcarrier.This helps to avoid power imbalances at the receivers for the detectionof the different transmission antennas after OFDM demodulation.

Finally, in an embodiment said frame forming means is adapted forinserting PAPR reducing methods (e.g. pilots, tone reservation carriers,etc.) for use by said further transmission antennas in bandwidthportions of said channel bandwidth covered by data segments onto whichdata blocks are mapped only in the SISO scheme. This provides for animprovement of the PAPR (peak-to-average power ratio) reduction of thetransmissions of the further transmission antennas.

In a further aspect of the present invention a transmission apparatus isprovided, in particular as described above, comprising at least twotransmission antennas, wherein a first transmission antenna is adaptedfor transmission of data blocks mapped onto data frames in any MIMO modeand wherein the further transmission antennas are adapted fortransmission of data blocks mapped onto data frames in the MISO schemeor MIMO scheme, wherein the one or more further antennas are adapted foralso transmitting data during times where the first transmission antennais transmitting data blocks mapped onto data frames in the SISO scheme,and wherein said further transmission antennas are adapted for eachsubstantially using the same transmission power as the firsttransmission antenna.

This transmission apparatus is generally provided for use in any kind oftransmission system, including broadcast systems, using at least twotransmission antennas in which different MIMO modes are alternately usedfrom time to time, i.e. where it is needed to quickly switch the one ormore further transmission antennas on and off. Such quick switchingoperations are thus avoided according to this aspect of the presentinvention.

Preferably, said one or more further antennas are adapted fortransmitting, during times when the first transmission antenna istransmitting data blocks mapped onto data frames in the SISO scheme, thesame data as the first antenna. This contributes to avoid undesiredpower variation among said one or more further antennas.

Also in such a transmission apparatus the further transmission antennasmay be adapted to use differently polarized subcarriers than the firstantenna. Further, in an embodiment the first and second transmissionantennas (in case of two transmission antennas may be inclined by +45°and −45°, respectively, to a vertical axis resulting in good receptionresults by a common rooftop antenna.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects of the present invention will be apparent fromand explained in more detail below with reference to the embodimentsdescribed hereinafter. In the following drawings

FIG. 1 shows a first embodiment of a mapping apparatus according to thepresent invention,

FIG. 2 shows a first embodiment of a transmitter according to thepresent invention,

FIG. 3 shows the structure of a complete T2-frame,

FIG. 4 shows more details of the structure of a complete T2-frame,

FIG. 5 shows an embodiment of a frame forming unit in accordance withthe DVB-T2 standard,

FIG. 6A shows a block diagram of a first embodiment of a frame formingunit in accordance with the present invention,

FIG. 6B shows a block diagram of a second embodiment of a frame formingunit in accordance with the present invention,

FIG. 6C shows a block diagram of a third embodiment of a frame formingunit in accordance with the present invention,

FIG. 6D shows a block diagram of a fourth embodiment of a frame formingunit in accordance with the present invention,

FIG. 7 shows a first embodiment of the frame structure of a secondframe,

FIG. 8 shows more details of the first embodiment of the frame structureof a second frame,

FIG. 9 shows the structure of a superframe,

FIG. 10 shows a second embodiment of the frame structure of the secondframe,

FIG. 11 shows a first embodiment for mapping signalling information intothe second frames,

FIG. 12 shows a second embodiment for mapping signalling informationinto the second frames,

FIG. 13 illustrates the steps of the method performed by a receiver forobtaining signalling information,

FIG. 14 shows a second embodiment of a mapping apparatus according tothe present invention,

FIG. 15 shows a second embodiment of a transmitter according to thepresent invention,

FIG. 16 shows a first embodiment of a broadcast system according to thepresent invention,

FIG. 17 shows an embodiment of a receiver of a first type used in saidbroadcast system shown in FIG. 16,

FIG. 18 shows a demapping apparatus of the receiver shown in FIG. 17,

FIG. 19 shows an embodiment of a receiver of second type according tothe present invention used in said broadcast system shown in FIG. 16,

FIG. 20 shows a demapping apparatus of the receiver shown in FIG. 19,

FIG. 21 shows a second embodiment of a broadcast system according to thepresent invention,

FIG. 22 shows another embodiment of a receiver according to the presentinvention used in said broadcast system shown in FIG. 21,

FIG. 23 shows a demapping apparatus of the receiver shown in FIG. 22,

FIG. 24 shows a third embodiment for mapping signalling information intothe second frames,

FIG. 25A shows a simplified diagram of a first embodiment of atransmitter according to the present invention,

FIG. 25B shows a simplified diagram of a second embodiment of atransmitter according to the present invention,

FIG. 26A shows a first example of a possible pilot pattern that may beused according to the present invention,

FIG. 26B shows a second example of a possible pilot pattern that may beused according to the present invention,

FIG. 26C shows a third example of a possible pilot pattern that may beused according to the present invention,

FIG. 27 shows a diagram illustrating a first embodiment how subcarriersare transmitted by two transmission antennas,

FIG. 28 shows a diagram illustrating a second embodiment how subcarriersare transmitted by two transmission antennas,

FIG. 29A shows a first embodiment of a broadcast system according to thepresent invention using different types of antennas in the transmissionapparatus,

FIG. 29B shows a second embodiment of a broadcast system according tothe present invention using different types of antennas in thetransmission apparatus,

FIG. 30A illustrates a transmission apparatus and the assignment oftransmission power to its transmission antennas, and

FIG. 30B illustrates a transmission apparatus and the assignment oftransmission power to its transmission antennas with constant powerallocation.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a block diagram of a mapping apparatus 10 according to thepresent invention. The apparatus 10 is provided for mapping payload dataof mapping input data streams S1, S2, . . . , Sn onto a mapping outputdata stream Q having a (predetermined) channel bandwidth fortransmission in a multi-carrier broadcast system. The mapping input datastreams S1, S2, . . . , Sn are each subdivided into data blocks (alsocalled bursts, sub-slices or data patterns) carrying payload data, whichare pre-processed by other elements of a transmitter as will beexplained below. A data input 12 receives said mapping input datastreams S1, S2, . . . , Sn. Further, signalling data Si are received bysaid data input 12.

For frame forming and mapping the data blocks of received mapping inputdata streams onto frames two different frame forming units 14 and 16 areprovided. A first frame forming unit 14 maps the data blocks of a firstgroup of mapping input data streams, e.g. of mapping input data streamsS1, S2 and S3, onto first frames F1 having a first frame structure alsocovering the total channel bandwidth. In addition, the signalling dataSi are incorporated into said first frames F1 for signalling therequired data to receivers of a first type that are adapted forreceiving and processing said first frames F1.

A second group of mapping input data streams, e.g. the mapping inputdata streams S1, S4 and S5, are provided to the second frame formingunit 16 which maps them onto second frames F2 having a second framestructure covering the total channel bandwidth. The second framestructure is generally different from the first frame structure, and thesecond frames F2 are generally provided for reception and processing bydifferent types of receivers. Also the second frame forming unit 16 usessignalling data Si for incorporation into the second frames F2 for useby the receivers, wherein the signalling data incorporated into thefirst frames F1 are generally different from the signalling dataincorporated into the second frames F2, which shall, however, notexclude that the same structure of the signalling data and thesignalling concept is used in both types of frames. Those frames F1, F2,in particular both sequences of first frames F1 and second frames F2generated by the first frame forming unit 14 and the second frameforming unit 16, are then further processed by a stream forming unit 18which alternately arranges one or more first frames F1 and one or moresecond frames F2, thus forming the mapping output data stream Q. Saidmapping output data stream is then outputted by a data output 20 forfurther processing and/or transmission.

FIG. 2 shows a block diagram of a transmitter 30 according to thepresent invention, in which a mapping apparatus 10 as explained above isused. FIG. 2 particularly shows an exemplary embodiment of a transmitter30 which, however, shall not be understood as limiting the applicationof the present invention.

The transmitter 30 comprises a first pre-processing unit 32 and a secondpre-processing unit 34. The first pre-processing unit 32 receivestransmitter input data streams I1, I2 . . . , Im and pre-processes themto obtain the mapping input data streams S1, S2, . . . , Sm. Thetransmitter input data streams I1, I2, . . . , Im may, for instance, beone or more (e.g. MPEG-2) transport stream(s) and/or one or more genericstream(s), and the data may be carried therein in individual PhysicalLayer Pipes PLPs.

The first pre-processing unit 32 is, in this exemplary embodiment,adapted in accordance with the DVB-T2 standard and comprises elementsfor input processing and Bit Interleaved Coding & Modulation (BICM).Such means may include means for CRC encoding, header insertion, paddinginsertion, scrambling, FEC encoding (LDPC/BCH) bit interleaving, bit tocell demultiplexing, cell to constellation mapping, constellationrotation and cyclic Q-delaying, cell interleaving and time interleaving,just to name a few elements that are generally provided as explained indetail in the DVB-T2 standard. Those elements are commonly known anddescribed in detail in the DVB-T2 standard so that no furtherexplanations are provided here.

The second pre-processing unit 34 is, in this exemplary embodiment,adapted for pre-processing the received transmitter input data streamsI1, I2, . . . , Ip, which may be different from, partly equal orcompletely equal to the transmitter input data streams I1, I2, . . . ,Im (which depends mainly on the kinds of services provided to thedifferent types of receivers). In an embodiment, said pre-processing maybe performed in the same or in a similar way as described in the DVB-T2standard (or, alternatively, in the DVB-C2 standard), possibly withadditional adaptions according to the needs of the desired application.Hence, said pre-processing unit 34 comprises, in this exemplaryembodiment, means for input processing and Bit Interleaved Coding &Modulation (BICM). Said means may particularly comprise means for inputstream synchronization, null packet detection, CRC-encoding, headerinsertion, scrambling, FEC (BCH/LDPC) encoding, bit interleaving, bit tocell demultiplexing, cell to constellation mapping and frame headerinsertion. Again, these means are generally known and described indetail in the DVB-T2 standard and the DVB-C2 standard so that no furtherexplanations are provided here.

It shall be noted that any time reference is made to any standardherein, the various explanations provided in the cited standard,particularly in the DVB-T2 standard and the DVB-C2 standard, to whichreference has been made above and will be made below, are hereinincorporated by reference herewith.

The output of the first and second pre-processing units 32, 34 are thenprovided as mapping input data streams S1, S2, . . . , Sm and S1, S2, .. . , Sp to the mapping apparatus 10, which is generally adapted asexplained above with respect to FIG. 1. In the particular embodimentshown in FIG. 2, however, the data input 12 is split-up into two datainput subunits 12 a, 12 b for respectively receiving the mapping inputdata streams from the first pre-processing unit 32 and the secondpre-processing unit 34. The mapping output data stream Q is thenprovided to a transmitter unit 36 for transmission, in particular by abroadcast, after further processing, where necessary.

Next, frame forming in the first frame forming unit 14 shall beexplained. If applied in transmitter 30 as depicted in FIG. 2, the firstframe forming unit 14 is also adapted to process the received mappinginput data streams S1, S2, . . . Sm in accordance with the DVB-T2standard. Hence, generally the first frame forming unit 14 comprises acell mapper, which assembles modulated cells of PLPs and signallinginformation into arrays corresponding to OFDM symbols. Hence, frames areformed (generally called “T2-frames”) as schematically depicted in FIG.3 and in more detail in FIG. 4. Such a T2-frame comprises one P1preamble symbol, followed by one or more P2 preamble symbols, followedby a configurable number of data symbols. Thereby, PLPs are classifiedinto three types, in particular common PLP, data PLP type 1 and data PLPtype 2. An exemplary embodiment of the first frame forming unit 14 isdepicted in FIG. 5. More details about the T2-frame structure and themapping of PLPs (generally referred to herein as mapping input datastreams) can be found in the DVB-T2 standard and shall thus not beprovided here.

Block diagrams of various embodiments of the second frame forming unit16 are schematically depicted in FIGS. 6A to 6D. A first embodiment ofthe second frame forming unit 16 a is shown in FIG. 6A. For each of thep mapping input data streams (PLPs) S1, S2, . . . , Sp received by thesecond frame forming unit 16 a a separate PLP processing unit 161 isprovided, each generally comprising a FEC-encoder 1611, an interleaver1612, a QAM-modulator 1613 (optionally with rotated constellations), anda MIMO mode selection unit 1614. Further, a signalling processing unit162 is provided for processing of signalling information, whichsignalling processing unit 162 generally comprises the same elements asthe PLP processing units 161. The processed PLPs and the processedsignalling data are then provided to one or more mapping units 163 a,163 b, whose task is the mapping of the time interleaving blocks of theseveral PLPs onto the frame structure. Therefore, each mapping unit 163a, 163 b divides the time interleaving blocks into bursts (generallycalled data blocks). These bursts are then mapped onto the OFDM symbols(generally called data symbols) in the different data slices (generallycalled data segments). The length of each burst is preferably a multipleof the number of useful OFDM subcarriers per data slice.

The data slices, more precisely the bursts of the data slices, are thensubjected to data slice processing including frequency interleaving anda pilot insertion, so that the complete OFDM symbol for thecorresponding data slice is generated. Preferably, a pairwise frequencyinterleaving is performed and all pilots are added, i.e. the scatteredand continual pilots for channel estimation and synchronization.Preferably, the bandwidth of the data slices is a multiple of 24, whichensures a constant number of payload OFDM subcarriers (generally perfour (temporally) consecutive segments). Generally, only after some(e.g. four) data symbols the pilot pattern is repeated, but not aftereach data symbol. This allows channel estimation in frequency and timedirection with reduced overhead.

The output from the data slice processing, the preamble, edge pilots andscrambling sequences, are then further processed. In particular, thedifferent data slices and the preamble are assembled to the completeframing structure to be used for the second frames F2. Furthermore, theedge pilot next to the highest OFDM subcarrier is added. Additionally,scrambling of the data is preferably performed. Finally, one or moreOFDM modulators 164 a, 164 b may be provided for OFDM modulation in eachprocessing path.

The MIMO mode selection unit 1614 provides the ability to select foreach mapping input data stream S1, S2, . . . , Sp individually the MIMOmode to be used for the data blocks of the respective mapping input datastream S1, S2, . . . , Sp. Hence, it can be determined for each mappinginput data stream S1, S2, . . . , Sp by which antenna configuration thedata blocks of the mapping input data stream S1, S2, . . . , Sp shall betransmitted. For instance, it may be determined that for the data blocksof the first mapping input data stream S1 the SISO scheme is selected,that for the data blocks of the second mapping input data stream S2 theMISO scheme is selected, and that for the data blocks of the thirdmapping input data stream S3 a MIMO scheme with spatial multiplexing isselected. For this purpose, more than one mapping unit 163 a, 163 b isprovided, which allows splitting the signal outputted from a PLPprocessing unit 161 onto various paths for individual processing, whichvarious paths are then provided to different transmission antennas. Forinstance, two transmission antennas (and, hence, two mapping units 163a, 163 b and two OFDM modulators 164 a, 164 b) may be provided, e.g. toallow the data to be split between the two transmission antennas on thesame frequency in such a way that the two transmission antennas will notmuch interfere with each other. In particular, e.g. in MISO scheme thepreprocessing of the signals is such that the receiver can separate thesignals, and in MIMO scheme both the receiver and the transmitter mayhave multiple antennas for reception and transmission, respectively,which numbers can be equal or different. This enables that eveninterfering signals can be reconstructed. More details as well asfurther examples will be explained below.

In another embodiment of the second frame forming unit 16 b illustratedin FIG. 6B for each mapping input data stream S1, S2, . . . , Sp aseparate buffer 165 is provided. These buffers 165 are filled with thedata blocks of the respective mapping input data stream. The mappingunit(s) 163 a, 163 b accesses the buffers 165, and when sufficient datablocks are stored in a buffer, e.g. for completely filling a data symbolof a data segment, these data blocks are taken from the buffer andprovided to the mapping unit(s) 163 a, 163 b for further processing andmapping onto said data symbol.

Further, according to this embodiment, a time and frequency interleaver1615 (e.g. implemented as separate units for time interleaving andfrequency interleaving) is provided in each PLP processing unit 161, andthe MIMO selection unit 1614 is further adapted for selecting the pilotpattern individually for each mapping input data stream S1, S2, . . . ,Sp. In this way, preferably the pilot density in time and/or frequencydirection can be selected, in particular depending on the number oftransmission antennas, to select the robustness of the data transmissionwith respect to reliable channel estimation at the receiver.

In still another embodiment of the second frame forming unit 16 cillustrated in FIG. 6C, which is quite similar to the embodiment of thesecond frame forming unit 16 b illustrated in FIG. 6B, a coding unit 166is provided in at least one (preferably all) mapping unit(s) 163 a, 163b. This coding unit 166 enables to encode the data blocks (e.g. all datablocks or selected data blocks), as is, for instance, regularlyperformed in MISO processing (for instance according to the DVB-T2standard). In an example an Alamouti code can be applied by the codingunit 166 on the data blocks outputted from the PLP processing unit 161to produce two similar sets of data blocks at the output, each of whichbeing directed to a separate transmission antenna.

Further, in this embodiment, for each mapping input data stream S1, S2,. . . , Sp a separate pilot pattern selection unit 1616 is provided forselecting the pilot pattern individually for each mapping input datastream S1, S2, . . . , Sp.

FIG. 6D shows still another embodiment of the second frame forming unit16 d. According to this embodiment the MIMO selection is not performedper mapping input data stream, but per data segment (also called dataslice). The output of the PLP processing units 161 is provided to ascheduler 167, whose task is the mapping of the time interleaving blocksof the several PLPs onto the frame structure. Therefore, the scheduler167 divides the time interleaving blocks into bursts. These bursts arethen mapped onto the OFDM symbols in the different data slices. Thelength of each burst is preferably a multiple of the number of usefulOFDM subcarriers per data slice. The data slices, more precisely thebursts of the data slices, are then provided to data slice processingunits 168, each comprising a frequency interleaver 1681 a MIMO modeselection unit 1682 and a pilot pattern selection unit 1683. The dataslice processing uses the data received from the scheduler 167, createsthe complete OFDM symbol for the corresponding data slice, and performsa pairwise frequency interleaving. Further, in the MIMO mode selectionunit 1682 the MIMO mode can be selected for all data blocks of therespective data stream, and in the pilot pattern selection unit 1683 thepilot pattern can be selected for all data blocks of the data stream.Preferably, the scheduler 167 is adapted such that it schedules onlydata blocks onto a particular data segment that shall be transmittedwith the same MIMO mode (and/or pilot pattern) of this particular datasegment.

The output from the data slice processing units 168, the preamble, edgepilots and scrambling sequences, are then provided to one or moreframing units 169, which assembles the different data slices and thepreamble to the complete framing structure to be used for the secondframes F2. Furthermore, it adds the edge pilot next to the highest OFDMsubcarrier. Additionally, it performs the scrambling of the data.Finally, one or more OFDM modulators 164 a, 164 b are provided for OFDMmodulation.

The embodiments illustrated in FIGS. 6A to 6D show that according to thepresent invention it is possible to select the MIMO mode and/or thepilot pattern individually for each mapping input data stream and/oreach data segment. It shall be understood that all possible combinationsof respective means for such a selection are possible.

According to embodiments of the present invention the selection of theMIMO mode and/or the pilot pattern and the mapping of the data blocksonto data symbols of the frame is performed such that the MIMO modeand/or the pilot pattern changes from data symbol to data symbol, from agroup of data symbols to a next group of data symbols (in timedirection), from frame to frame, from a group of frames to a next groupof frames, from data segment to data segment and/or from a group of datasegments to a next group of data segments.

The frame structure of the second frames F2 as generated by suchembodiments of the second frame forming unit 16 is schematicallydepicted in FIG. 7 and in more detail in FIG. 8.

These figures show the frame structure of the second frame F2 as definedin the DVB-C2 standard. This frame structure uses the concept ofabsolute OFDM, according to which all frequencies are aligned to theabsolute frequency 0 MHz, which is identical to the OFDM subcarrierindex k=0. The OFDM subcarrier frequencies of the following OFDMsubcarriers are given by f=(1/T_(u))·k, where T_(u) is the duration ofthe useful OFDM symbol part. Hence, the start and stop frequencies ofthe signal can also be given in OFDM subcarrier indices instead of amiddle frequency of the signal. The start and the stop frequency aregiven by K_(min) and K_(max), respectively. It shall be noted, however,that the used of absolute OFDM is not essential for the presentinvention.

It is important to note that the concept of absolute OFDM can be used,but must not necessarily be used. For instance, in an embodiment, boththe first and second frames F1, F2 are aligned to a frequency raster anduse the concept of absolute OFDM, whereas in another embodiment both thefirst and second frames F1, F2 are not aligned to a frequency raster anddo not use the concept of absolute OFDM. The second frames F2, however,make use of the concept of segmented OFDM as illustrated in FIGS. 7 and8, while the first frames F1 generally do not make use of this concept(but could also use it in certain embodiments).

The frame F2 has a preamble portion 40 and a payload portion 50. Thesignalling data are mapped on the preamble portion 40, which comprises(in time direction) one or more preamble symbols 41 (e.g. L_(p) preamblesymbols 41 as shown in FIG. 8). Each preamble symbol 41 carries (infrequency direction) one or more preamble signalling blocks 42 (alsocalled L1 block symbol) which carry the signalling data, i.e. the samesignalling data are included therein and are thus periodically repeated,although the signalling blocks 42 are not completely identical, e.g. dueto the use of different pilots therein.

The payload portion 50 is segmented into data segments 51 (also calleddata slices, e.g. 5 data slices as shown in FIG. 7 or k data slices asshown in FIG. 8. Each data segment 51 carriers a number of data symbols52, e.g. L_(Data) data symbols as shown in FIG. 8). Onto these datasymbols the data blocks of the various mapping input data streams S1,S2, . . . , Sp are mapped. Various embodiments of said mapping will beexplained in more detail below.

As can also be seen from FIGS. 7 and 8 the preamble segments 43, intowhich the preamble portion is segmented in frequency direction, all havean equal bandwidth which is equal to or larger than the bandwidth of thedata segments 51. This shall be understood as an example only, thebandwidth of the preamble segments 43 can also be smaller than thebandwidth of the data segments 51, e.g. if less signalling informationmust be put into the preamble segments. Generally, the bandwidth of boththe preamble segments and the data segments is smaller than or equal tothe receiver bandwidth. There is also no necessity of any alignment ofthe beginning of the preamble segments 43 with the beginning of the datasegments in a frequency domain. Hence, a transmitter may also onlytransmit two partial preamble signalling blocks 42, for which thereceiver can create a complete preamble signalling block if it knowswhere these preamble signalling blocks begin.

FIG. 9 shows a superframe structure that is formed by the stream formingunit 18 from the first and second frames, F1, F2. In particular, byalternately arranging one or more first frames F1 and one or more secondframes F2 said superframe structure is formed. The sequence of saidsuperframes F3 then represents the mapping output data stream Qoutputted by the stream forming unit 18 via the data output 20.

Adopting the superframe structure as defined in the DVB-T2 standard thefirst frames F1 represent the T2-frames, and the second frames F2 areplaced into the parts reserved for the FEF frames. For instance, in apractical embodiment the F1 frames (formed in accordance with the DVB-T2standard) are provided for reception by stationary receivers (e.g. inaccordance with the DVB-T2 standard), and the second frames F2 (e.g.formed in accordance with a DVB-C2 standard or according to any newrules) are provided for reception by mobile receivers (e.g. according tothe upcoming DVB-NGH standard).

Next, embodiments for mapping the data blocks of a mapping input datastream onto the second frame F2 shall be explained. In a firstembodiment, which is generally in consistence with the frame structuredefined in the DVB-C2 standard, the data blocks of a particular mappinginput data stream are mapped onto a single data segment or two or more(neighbouring or not neighbouring) data segments. For instance,referring to FIG. 7, all data blocks of a particular mapping input datastream are thus mapped on (for instance) data slice 1 or data slices 1and 2. This has the advantage that the receiver tuning position can bekept fixed once the receiver has tuned to the data segment it wants toreceive.

According to another embodiment as schematically depicted in FIG. 10,the data blocks of a particular mapping input data stream are spread intime and frequency over various data symbols and various data segments.For instance, the data symbols 52 a-52 e indicated in FIG. 10 carry datablocks of a particular mapping input data stream and are spread infrequency over the five data segments 51 a-51 e and in addition in timeso that at each time only one data segment carries a data symbolcontaining data of said particular mapping input data stream. Thisprovides the advantage of an increased robustness due to increased timeand frequency diversity. Of course, the tuner of the receiver has towake up slightly earlier for channel estimation if the data blocks ofthe data stream it wants to receive are spread over various datasegments. If time-slicing (as in DVB-H or DVB-T2) is applied, thisproblem always occurs. However, the retuning to new frequencies shouldonly induce a small overhead in processing and power consumption(compared to always-on and full-bandwidth tuning).

In a single data segment data blocks belonging to various mapping inputdata streams can thus be transmitted according to this embodiment of thepresent invention. These data blocks may be pre-processed in the samemanner, but also in different manner (e.g. with different MODCODs) toprovide different levels of robustness to the different mapping inputdata streams. For instance, as proposed according to an embodiment ofthe present invention, different MIMO modes and/or different pilotpatterns may be applied to the data blocks of the individual mappinginput data streams. Further, in an alternative or in addition, differentMIMO modes and/or different pilot patterns may be applied to the datablocks mapped onto the individual data segments.

While it is generally possible, that at a particular time also more thanone data symbol (i.e. from different data segments) carry a data blockof the same mapping input data stream, the embodiment shown in FIG. 10is preferred since in this case receivers with smaller bandwidths can beused.

The mapping structure of the data blocks of a particular mapping inputdata stream can be kept regular, as shown in FIG. 10, but is preferablyselected irregular, i.e. the data blocks are preferably spreadirregularly over the data symbols of the second frame F2 and notaccording to any regular (e.g. periodic) pattern in time and/orfrequency. This also contributes to an increased robustness,particularly against regular disturbances. This requires an increasedamount of signalling information needed for the receiver to find thedata symbols of the mapping input data stream to be received. For thisproblem, however, several solutions exist as will be explained below.

Further, time gaps are preferably introduced between data blocks of amapping input data stream, during which no data symbol of any datasegment carries a data block of said particular mapping input datastream. For instance, as shown in FIG. 10, there is a time gap Δtbetween the data symbols 52 c and 52 d, during which other data symbolsare provided, which, however, do not carry data blocks of the mappinginput data stream whose data blocks are carried in the data symbols 52a-52 e. This provides the advantage that a receiver might fall intosleep mode during this time gap Δt to save power. Generally, said timegap Δt is preferably large enough to allow the receiver to fall intosleep mode, wake up timely and re-tune, but it might differ from datasymbol to data symbol. It is at least large enough to allow the receiverto re-tune.

The bandwidth of the data segments 51 may be kept equal andpredetermined, as shown in FIG. 10. However, in other embodiments thebandwidth of the individual data segments 51 may be variable or may bedetermined as needed. For instance, if a mapping input data stream hasonly a low amount of data compared to other mapping input data streams adata segment might be used having a smaller bandwidth for said mappinginput data stream.

According to still another embodiment of the mapping, the mapping ofdata blocks of a particular mapping input data stream may be keptconstant within a particular frame F2, but may be changed from frame F2to the next frame F2, i.e. a frequency hopping may be provided fromframe to frame (or from a first group of frames to the next group offrames), but not within frames.

According to still another embodiment a data block can be split up infrequency direction for use by data symbols from different mapping inputdata streams. This is illustrated in FIG. 10 by use of data symbol 54.In this example, the data symbol is split up into a first partial datasymbol 54 a, onto which a first (possibly partial) data block from afirst mapping input data stream is mapped, and a second partial datasymbol 54 b, onto which a second (possibly partial) data block from asecond mapping input data stream is mapped. This, for instance, makessense if the total data symbol 54 cannot be filled by a complete datablock from the first mapping input data stream (e.g. because not enoughdata are currently available).

Next, various embodiments for signalling the required signallinginformation about the mapping of the data blocks onto the data segmentsand the data symbols of the second frames shall be explained. In a firstembodiment only the preamble signalling blocks comprise all thesignalling information required for a transmitter to receive and demapall the intended data blocks. This embodiment would, however, requirethat the preamble signalling blocks are quite large (in frequency and/ortime), since the preamble has typically a high pilot density for robustchannel estimation and synchronization leading to the result that lesssignalling capacity is available in the preamble. Hence, putting a lotof signalling information into the preamble signalling blocks wouldfurther increase their size, which is generally not preferred.

In another embodiment, illustrated in FIG. 11, where a second frame F2is shown having a preamble portion 40 and a another preamble portion 45(often also referred to as “postamble”; generally contains the sameinformation as the preamble portion 40, but indicating that it isanother preamble portion, i.e. a “postamble portion”), the signallingprinciple is based on two steps. The preamble signalling blocksaccording to this embodiment comprise only high level, rough signallinginformation about the mapping of the data blocks onto the data segments.This high level signalling information may correspond to the signallingparameters that are generally transmitted in the initial layer 1 blocks,as commonly done according to the DVB-T2 or DVB-C2 standard. This highlevel information may, for instance, comprise information about thebandwidth of the data segments in the payload portion, the used pilotpatterns, the guard interval etc. In addition, it comprises preferably apointer block 44 including at least one pointer to at least one payloadportion signalling block 53, which is provided in the payload portion 50and which comprises low level, more detailed signalling informationabout the mapping of the data blocks onto the data symbols of the secondframe. This payload portion signalling block 53 a shown in FIG. 11 thusrequires sufficient information for the receiver to find and decode thedata symbols carrying data blocks of the desired data stream. Further, apointer to the next payload portion signalling block 53 b may beincluded which comprises further information, particularly regarding thelocation of subsequent data symbols carrying payload data.

As shown in FIG. 11 each payload portion signalling block 53 a-53 fpoints to the next payload portion signalling block, which payloadportion signalling blocks can thus be mapped and decoded basically inthe same way as the data blocks carrying actual payload data. Thepointer from one payload portion signalling block to the next payloadportion signalling block may also point across other frames F1 locatedin between two second frames F2.

According to another embodiment multiple pointers are included in thepointer block 44, which point to several payload portion signallingblocks, e.g. to the payload portion signalling blocks 53 a-53 c. Afterdeinterleaving and decoding said payload portion signalling blocks 53a-53 c sufficient low level signalling information and locationinformation (e.g. pointers) for finding the next set of payload portionsignalling blocks 53 d-53 f as well as the next group of data blocks.Thus, according to such an embodiment, a set of pointers is transmittedduring several bursts (i.e. payload portion signalling blocks) andprovides information on the next bursts (i.e. payload portion signallingblocks) of the following set as well as the next data blocks.

Another embodiment for signalling shall be explained with reference toFIG. 12 showing a single second frame F2. According to this embodimentthe signalling principle is based on three steps. Firstly, as mentionedabove, the preamble signals the position of at least the first payloadportion signalling block 53 a provided in the payload portion 50. Forthis purpose, again, the preamble may comprise a pointer 44. Thereceiver is then able to decode the (one or more) payload portionsignalling block(s) 53 a (53 b, 53 c), which carries the data requiredfor decoding the data blocks of the mapping input data streams.Preferably, the payload portion signalling blocks are mapped onto theframe F2 and transmitted similar to the data blocks carrying payloaddata, which allows for long time interleaving and robustness.

Still further, according to this embodiment, at least one of saidpayload portion signalling blocks 53 a-53 c (or the whole set together,in particular after deinterleaving and decoding) provides information,in particular a pointer, by which the receiver finds at least the firstdata block 52 a (or the group of next data blocks) of the desired datastream. Said data block 52 a does not only contain the actual payloaddata, but also contains in-band signalling information comprising lowlevel, more detail signalling information about the mapping of the datablocks of said particular mapping input data stream onto the datasegments of the frames. This in-band signalling information thus enablesthe receiver to find the next data block 52 b of the same data stream.Hence, from this moment on the receiver is no longer obliged to receiveand decode the signalling information comprised in the preamble and/orin the payload portion signalling blocks, but the in-band signallinginformation contained in the data blocks 52 a, 52 b, . . . is sufficientfor finding all data blocks of the desired data stream and maybe also ofother “related” data streams (for enabling faster zapping to relatedservices).

According to a modification of said embodiment, not each single datablock contains sufficient information for finding the next data block,but several data blocks 52 a, 52 b are treated as a unit. Only afterdeinterleaving and decoding all of them, the in-band signallinginformation is available including information about the next “unit”(i.e. group of data blocks).

Hence, generally the receiver is not obligated to receive the preambleor the payload portion signalling blocks, which may again be consideredas a separate signalling data stream mapped onto the payload portion ofthe frame. However, if the position of the data blocks is not known atthe time the current mapping input data stream was encoded, it can alsopoint to the position of the next payload portion signalling block. Itshall be noted that the payload portion signalling blocks do generallynot only comprise signalling information for a single mapping input datastream, but for all mapping input data streams.

Hence, according to this embodiment the signalling information specificto a particular mapping input data stream is provided in-band in thedata blocks of said mapping input data streams, e.g. attached at thebeginning or at the end of the data blocks. It is also possible tointerleave said signalling information together with the FEC-encodeddata blocks by a common interleaver, or the signalling information maybe combined with the uncoded payload data (either completely at thebeginning or end or sub-divided into several portions), and then acommon FEC-encoding followed by interleaving is performed, preferably byuse of a common interleaver, i.e. over multiple FEC-coded blocks. Thisprovides the advantage of longer time diversity and, after theseparation into various data segments, also more frequency diversity.

According to the present invention, further information is preferablyincluded in the signalling information, in particular in the payloadportion signalling blocks, which informs the receiver about the selectedMIMO mode per mapping input data stream and/or per data segment and, ifrequired, about the selected pilot pattern per mapping input data streamand/or per data segment.

A simple block diagram illustrating the steps for retrieving of thesignalling information in the receiver, if the signalling information ismapped onto the frame F2 as illustrated in FIG. 12, is shown in FIG. 13.In a first step 80 the preamble is detected, which is mainly used forinitial synchronization to the data stream to be received. A pointer inthe preamble points to the next payload portion signalling block, whoseposition is obtained in step 81 by decoding the preamble, at least thepointer included therein. In this embodiment the payload portionsignalling blocks are mapped onto the frame F2 like a normal mappinginput data stream and are also called “signalling PLP”. In step 82 thispayload portion signalling block of the signalling PLP is received anddecoded. Afterwards, the complete signalling is done in-band, i.e.within the mapping input data stream itself. Hence, in step 83, theservice and the position of the next data block (also called payloadburst) is obtained and decoded.

It shall be noted that the same principles and the same embodiments forsignalling information can be used if the pointer unit 44 is included inthe other preamble 45 (i.e. the postamble) of a frame.

The preferred embodiment of a receiver only needs to obtain thesignalling information stored in a preamble portion, then accesses apayload portion signalling block a single time, and from then on usesonly the in-band signalling information. The in-band signallinginformation preferably includes a pointer to the next data block of thedata stream and to the next payload portion signalling block (which isuseful if a payload portion signalling block is provided in every frameof the same type, but is otherwise not needed since then enough preamblesymbols are in between from which the signalling information can also beprovided in some embodiments). Only, if the receiver wants to switch toanother service, a payload portion signalling block has to be accessedagain a single time to obtain the required signalling informationrelated to the new service.

An example of the signalling information that can be included in thepayload portion signalling blocks is illustrated in the following table,where the entries are either self-explaining, or as defined in the T2standard, or as described below:

FRAME_NUMBER: This 8-bit field indicates the frame number of the lastburst of the time interleaving frame.NUM_PLP: This 8-bit field signals the number of PLPs present in thecurrent DVB-NGH signal. The following fields appear for every signalledPLP:

-   -   PLP_ID: 8-bit identifier of the PLP.    -   PLP_IDENTIFICATION: This 16-bit field uniquely identifies a PLP        within a network.    -   PLP_QAM_MODE: This 4-bit field signals the QAM mode of the PLP        (including rotated constellations).    -   PLP_FEC_MODE: This 4-bit field signals the FEC mode of the PLP        (including FEC code length).    -   PLP_MIMO_MODE: This 2-bit field signals the MIMO mode of the PLP        according to the following table:

TABLE 1 PLP_MIMO_MODE field PLP_MIMO_MODE 00 01 10 11 mode SISO MISOMIMO reserved

-   -   PLP_PILOT_PATTERN: This 3-bit field identifies the pilot pattern        in which the PLP is transmitted.    -   PLP_TYPE: This 8-bit field indicates the PLP type.    -   PLP_PAYLOAD_TYPE: This 8-bit field signals the payload type,        e.g. TS, GSE.    -   NUM_ASSOCIATED_PLP: This 3-bit field indicates the number of        PLPs that are associated with this PLP.

The following two fields appear for each associated PLP:

-   -   ASSOCIATED_PLP_ID: This 8-bit field indicated the PLP ID of the        associated PLP.    -   ASSOCIATION_TYPE: This 2-bit field signals the association type,        e.g. local service or incremental redundancy.    -   INTERLEAVING_TYPE: This 2-bit field indicates the time        interleaver type.    -   NUM_SIGNALLED_TI_FRAMES: This 2-bit field indicates the number        of signalled time interleaving frames for the given PLP minus 1,        so NUM_SIGNALLED_TI_FRAMES=0 corresponds to one TI frame.

The following fields appear for each signalled time interleaving frame:

-   -   TI_NUM_(—) BURSTS: This 3-bit field signals the number of bursts        for the given time interleaving frame.    -   TI_FRAME_NUMBER: This 8-bit field indicates the frame number in        which the time interleaving frame starts. If the number is        smaller than the frame number of the current frame, the        TIFRAME_NUMBER refers to the following super frame.    -   INTRASYMBOL POINTER: This 11-bit field points to the start of        the time interleaving frame within an OFDM symbol.

The following fields appear for each time interleaving burst:

-   -   DATA_SLICED_ID: This 4-bit field indicates the Data Slice number        containing the burst.    -   PILOT_PATTERN: This 3-bit field indicates the pilot pattern used        in the given data slice. In case of a postamble, this signalling        gets valid for the next frame.    -   OFDM_SYMBOL_NUMBER: This 8-bit field indicates the OFDM symbol        number of the next given burst. If the number is lower than the        number of the previous burst, this burst is transmitted within        the next frame.

The following field only appears if there are associated PLPs:

-   -   ASSOCIATED_PLP_IDX: This 3-bit field indicates the index of the        associated PLP in the NUM_ASSOICATED_PLP loop. A value of 0        means that no PLP is currently associated.    -   TIME_INTERLEAVER_SIZE: This 8-bit field indicates the length of        the time interleaving frame in multiples of LDPC codewords.    -   NUM_HANDOVER_PLP: This 8-bit field indicates the number of PLPs        that will be signalled in the handover signalling.

The following fields appear for every signalled handover PLP.

-   -   PLP_IDENTIFICATION: This 16-bit field uniquely identifies the        PLP within a network.    -   NUM_ALTERNATIVE_CELLS: This 8-bit field indicates the number of        alternative cells within the given network that also carry the        PLP.

The following fields appear for every alternative cell:

-   -   START FREQUENCY: This 24-bit field indicates the start frequency        of the alternative cell.    -   CELL_ID: This 16-bit field indicates the cell ID of the        alternative cell.    -   CRC32: This 32-bit cyclic redundancy check ensured correctness        of the data.

FIELD SIZE FRAME_NUMBER 8 bit NUM_PLP 8 bit for i = 1 ... NUM_PLP { PLP_ID 8 bit  PLP_IDENTIFICATION 16 bit   PLP_QAM_MODE 3 bit PLP_FEC_MODE 4 bit  PLP_MIMO_MODE 2 bit  PLP_PILOT_PATTERN 3 bit PLP_TYPE 8 bit  PLP_PAYLOAD_TYPE 8 bit  NUM_ASSOCIATED_PLPs 3 bit  ForNUM_ASSOCIATED_PLPs {   ASSOCIATED_PLP_ID 8 bit   ASSOCIATION_TYPE 2 bit }  INTERLEAVING_TYPE 2 bit  NUM_SIGNALLED_TI_FRAMES 2 bit  for i = 1...   TI_NUM_BURSTS 3 bit   TI_FRAME_NUMBER 8 bit   INTRASYMBOL_POINTER11 bit    for i = 1 ... NUM_BURSTS {    DATA_SLICE_ID 4 bit   OFDM_SYMBOL_NUMBER 8 bit    PILOT_PATTERN 3 bit    if(NUM_ASSOCIATED_PLP > 0) {     ASSOCIATED_PLP_IDX 3 bit    }   }  TIME_INTERLEAVER_SIZE 8 bit  } } NUM_HANDOVER_PLPs 8 bit for i = 1 ...NUM_HANDOVER_PLPs {  PLP_IDENTIFICATION 16 bit   NUM_ALTERNATIVE_CELLS 8bit  for j = 1 ... NUM_ALTERNATIVE_CELLS {   START_FREQUENCY 24 bit   CELL_ID 16 bit   } } CRC32 32 bit 

A further embodiment for signalling information is illustrated withreference to FIG. 24. According to this embodiment payload portionsignalling blocks 53 a-53 c are mapped onto data symbols of the secondframe 50 a. Into these payload portion signalling blocks 53 a-53 csignalling information, in particular pointers, about the mapping of thedata blocks 55 d-55 f, 56 d-56 f of the various data streams (55 a-55 fbeing data blocks of a first data stream, and 56 a-56 f being datablocks of another data stream) onto the data symbols of a subsequentgroup of second frames (or only a single second frame), here the nextsecond frame 50 b, have been included. Hence, in a group of one or moresecond frames (e.g. the frame 50 a) all the required signallinginformation can be found by the receiver in one or more of the payloadportion signalling blocks 53 a-53 c, that are required to find all datablocks 55 d-55 f, 56 d-56 f carrying payload data mapped onto thesubsequent group of (one or more) second frames 50 b. Instant zapping ofthe receiver between all data streams is thus possible within thesubsequent group of (one or more) second frames 50 b without any waitingtime for first obtaining the required signalling information.

Additionally, some offset signalling information 57 a, 57 b indicatingchanges of the mapping of the data blocks 55 a-55 f, 56 a-56 f betweensaid particular group of second frames 50 a and said subsequent group ofsecond frames 50 b can be included into in-band signalling informationor into one or more payload portion signalling blocks mapped onto datasymbols of said particular second frame. Hence, at the end of a group of(one or more) second frames said offset signalling information 57 a canbe mapped as in-band signalling information into one or more data blocks55 c, 56 c. Alternatively, said offset signalling information 57 b canbe mapped into one or more payload portion signalling blocks 53 c. Saidoffset signalling information 57 a, 57 b indicates how the signallinginformation changes from this group of second frames 50 a to the nextgroup of second frames 50 b (or any other subsequent frame) so that inthe next (or subsequent) group(s) of second frames 50 b all thesignalling information must not necessarily be mapped into payloadportion signalling blocks or must at least not be obtained by thereceiver. In other words, mainly some offset information is mapped intothe frames, particularly to save time (in the receiver).

Another embodiment of a mapping apparatus 60 according to the presentinvention is schematically depicted in FIG. 14. A correspondingtransmission apparatus 70 comprising such a mapping apparatus 60 isdepicted in FIG. 15. The main difference between the mapping apparatus60 shown in FIG. 14 and the mapping apparatus shown in FIG. 1 is thataccording to the embodiment of the mapping apparatus 60 shown in FIG. 14only a single frame forming unit 64 is provided following the data input62 and that no stream forming unit 18 is provided. Said frame formingunit 64 basically corresponds to the second frame forming unit 16 asshown in FIG. 1, but is adapted for mapping the data blocks of themapping input data streams S1, S2, . . . , Sn onto frames F having aframe structure as shown in FIG. 10 for the second frames F2.

In other words, the data blocks are mapped onto said frame F such thatthey are spread in time and frequency over various data symbols andvarious data segments of the frame F2 as shown in FIG. 10 or as furtherexplained above regarding further variations of the frame structure forthe frame F2. Thus, said frame structure applied by the frame formingunit 64 provides a time and frequency diversity enabling the use of anarrow-band receiver and providing the desired low power consumption ofthe receiver. The generated frames F are generally arranged sequentiallyand are then outputted by the data output 66 as mapping output datastream Q for further processing and/or transmission.

The transmitter 70 shown in FIG. 15 differs from the transmitter 30shown in FIG. 2 in that it only comprises a single pre-processing unit72 which basically corresponds to the pre-processing unit 34, accordingto which the input data streams I1, I2, . . . , In are processed asdefined in the DVB-T2 or DVB-C2 standard. Of course, the pre-processingmay also be employed in a different way and must not necessarily beconsistent with the DVT-T2 or DVB-C2 standard (or any standard). Fortransmission of the mapping output data stream Q a transmitter unit 74is provided which generally corresponds to the transmitter unit 36 shownin FIG. 2.

It shall be noted that the frame forming unit 64 shown in FIG. 14generally corresponds to the second frame forming unit 16 shown inFIG. 1. In particular, for the frame forming unit 64 the sameembodiments exist as have been explained above for the second frameforming unit 16 and as have been shown in FIGS. 6A to 6D. Further, theembodiments illustrated in FIGS. 6A to 6D are to be understood only asexamples of possible implementations. Further embodiments existincluding other combinations of the preferred elements, in particularthe MIMO mode selection units, the pilot pattern selection units, thecoding unit and the buffer units.

FIGS. 25A and 25B schematically illustrate two preferred embodiments ofthe transmitter according to the present invention in a simplifieddiagram and by use of two simple examples showing only a few elements ofthe transmitter.

In the first embodiment of the transmitter 70 a shown in FIG. 25A threemapping input data streams S1, S2, S3, e.g. representing three differentservices that shall be available to mobile receivers, are illustrated.The first mapping input data stream S1, e.g. a movie service, isprovided to a first MIMO mode selection unit 1614 a, which selects thatMIMO processing shall be applied to the data blocks of this firstmapping input data stream S1. Accordingly, the data stream Si is splitoff into (at least) two output streams S11, S12, which may be codeddifferently (e.g. by spatial multiplexing, e.g., according to the D-/H-or V-BLAST (Bell Labs Layered Space Time scheme) architecture; notshown) and which are provided to different mapping units 163 a, 163 b.Therein, the data blocks of said output streams S11, S12 are mapped ontodifferent mapping output data streams Qa, Qb, which are provided todifferent transmission antennas 76 a, 76 b for broadcasting. Forreceiving these data blocks the receiver uses two reception antennas andtwo reception paths to individually process the received mapping outputdata streams Qa, Qb until they are combined to obtain the informationcontained in the received service (i.e. in the data stream S1). SinceMIMO processing is applied to this service, a high throughput of thedata transmission can be obtained. Generally, this depends on the MIMOscheme: spatial multiplexing is for higher throughput, while otherspace-time (or space-frequency) MIMO schemes aim for higher robustness.

The second mapping input data stream S2, e.g. a news service, isprovided to a second MIMO mode selection unit 1614 b, which selects thatMISO processing shall be applied to the data blocks of this secondmapping input data stream S2. Accordingly, the data stream S2 is splitoff into (at least) two output streams S21, S22, which may be codeddifferently (e.g. by an Alamouti encoder; not shown) and which areprovided to different mapping units 163 a, 163 b. Therein, the datablocks of said output streams S21, S22 are mapped onto the differentmapping output data streams Qa, Qb, which are provided to the differenttransmission antennas 76 a, 76 b for broadcasting. For receiving thesedata blocks the receiver generally only requires a single receptionantenna and a single reception path to process the received mappingoutput data streams Qa, Qb until they are combined to obtain theinformation contained in the received service (i.e. in the data streamS2). Thus, this news service can be detected by any receiver(independent of the number of deployed receive antennas) and thetransmission is reliable, because of the MISO scheme.

The advantages of MISO vs. MIMO are the high robustness and simpledetection (1 reception antenna is sufficient). The robustness of MISOcan be further increased if MIMO is used with the same data rate as witha single transmission antenna. On the other hand, the performance ofspatial multiplexing MIMO drops rapidly if the spatial distributioncoefficients (channel coefficients) are correlated. This is, forinstance, the case if the antennas are located close to each other, asis e.g. the case in a small handheld device having two antennas. Incontrast, a MISO method has in worst case (completely correlated channelcoefficients) the same performance as a SISO method.

The third mapping input data stream S3, e.g. a music service, isprovided to a third MIMO mode selection unit 1614 c, which selects thatSISO processing shall be applied to the data blocks of this secondmapping input data stream S3. Accordingly, the data stream S3 isprocessed into a single output stream S31, which is provided to at leastone of said mapping units 163 a, 163 b. Generally, mapping of the datablocks of said output stream S31 onto one mapping output data stream Qaor Qb and transmission over one transmission channel is sufficient.Preferably, however, the identical data blocks are mapped onto bothmapping output data streams Qa, Qb and are thus also broadcast by alldifferent transmission antennas 76 a, 76 b as is typically done insingle frequency networks. Again, for receiving these data blocks thereceiver generally only requires a single reception antenna and a singlereception path to process the received mapping output data streams Qa,Qb until they are combined to obtain the information contained in thereceived service (i.e. in the data stream S3). Compared to MIMO and MISOthe described SISO method has the advantages of simple detection, inparticular with respect to channel estimation, and less energyconsumption.

While in the embodiment of the transmitter 70 a the selection of theMIMO mode is available per mapping input data stream, in the embodimentof the transmitter 70 b shown in FIG. 25B the selection of the MIMO modeis available per data segment. Accordingly, after preprocessing themapping input data streams S1, S2, S3 by PLP processing units 161 a, 161b, 161 c (see also FIG. 6D) and scheduling by the scheduler 167, MIMOmode selection is performed per data segment 51 a, 51 b, 51 c by MIMOmode selection units 1682 a, 1682 b, 1683 c. Therein, generally the samefunction is performed as explained above with respect to the MIMO modeselection units 1614 a, 1614 b, 1614 c, but now on the level of datasegments. Thereafter the data blocks of the various obtained datasegments 51 aa, 51 ab, 51 ba, 51 bb, 51 ca are provided to the mappingunit 163 as, 163 b, wherein they are mapped accordingly on the mappingoutput data streams Qa, Qb and then transmitted by the transmissionantennas 76 a, 76 b.

Further embodiments of the transmitter include pilot pattern selectionmeans in addition or instead of MEMO mode selection means. For instance,the MIMO mode selection means shown in FIGS. 25A, 25B can be replaced orcomplemented with such pilot pattern selection means for selecting thepilot pattern per mapping input data stream and/or per data segment.

For allowing channel estimation scattered pilots are added to the dataslices. The addition of these scattered pilots is already done withinindividual data slices, as it is possible to have different pilotdensities within different data slices of the same signal.

The equalisation of SISO signals requires the estimation of a singlechannel transfer function, only. However, as the neighbouring dataslices may use MIMO or MISO signals, the edge pilots and the preamblepilots carry MIMO or MISO pilots. Though, edge pilots and preamblepilots are not part of the data slice pilots. Different pilot densitiescan be supported. The pilot patterns PP0 and PP1 are intended for largeSingle Frequency Networks, while the pilot schemes PP2 and PP3 havereduced overhead. Furthermore, PP0 and PP2 are optimized for high speedreception, as they have an increased pilot density in the timedirection. In another embodiment the edge pilot density is selected withthe highest possible density of a complete data segment, a completeframe or the complete data transmission.

Within a data slice a given cell is a scattered pilot if

k _(DS) mod(D _(X) ·D _(Y))=D _(X)(l mod D _(Y)) k=1, . . . , N _(DS-1),

where k_(DS) is the subcarrier number within the data slice, and l isthe symbol number within the frame, respectively. Further, Dx indicatesthe difference in carrier index between adjacent scattered-pilot-bearingcarriers and Dy indicates the difference in symbol number betweensuccessive scattered pilots on a given carrier. The values for D_(X) andD_(Y) are given in the following table:

Pilot Pattern D_(X) D_(Y) PP0 4 2 PP1 4 4 PP2 8 2 PP3 8 4

FIG. 26A shows an example pilot arrangement for pilot pattern PP0.

The modulation sequence of the pilots is

Re{c′ _(m,l,k) _(DS) }=A _(SP) and Im{c′ _(m,l,k) _(DS) }=0,

where A_(SP) is the boosting level of the scattered pilots as defined inthe following table.

Pilot Pattern A_(SP) PP0 4/3 PP1 4/3 PP2 4/3 PP3 7/4Furthermore, no scrambling is applied at this point as the completescrambling is performed in the framing section.

The transmission of MIMO or MISO services requires additional pilots, astwo different channel transfer functions have to be estimated by thereceiver. However, in contrast to DVB-T2, the possibility to supportalso large Single Frequency Networks shall be provided. Hence, anadditional pilot pattern is overlaid to the SISO pilots, i.e. theinverted pilots. Hence, a cell is a non-inverted pilot if

k _(DS) mod(D _(X) ·D _(Y))=D _(X)(l mod D _(Y)) k=1, . . . , N _(DS)−1,

and an inverted pilot if

k _(DS) mod(D _(X) ·D _(Y))=D _(X)[(l+D _(Y)/2)mod D _(Y) ] k=1, . . . ,N _(DS)−1,

where the values D_(X) and D_(Y) are again defined in the above table.The modulation sequence for the transmitters of MIMO OR MISO group 0 is:

Re{c ^(0,) _(m,l,k) _(DS) }=A _(SP) and Im{c ^(0,) _(m,l,k) _(DS) }=0.

The modulation sequence for the non-inverted pilots of MIMO or MISOgroup 1 is:

Re{c ^(1,) _(m,l,k) _(DS) }=A _(SP) and Im{c ^(l,) _(m,l,k) _(DS) }=0,

while the modulation sequence for the inverted pilots of MIMO or MISOgroup 1 is:

Re{c ^(l,) _(m,l,k) _(DS) }=−A _(SP) and Im{c ^(l,) _(m,l,k) _(DS) }=0.

The values for A_(SP) are again given in the above table. Furthermore,FIG. 26B depicts an arrangement of the MIMO or MISO pilots for pilotpattern PP0.

The edge pilots are generally selected such that they are fitting withthe pilot patterns of one or more neighbouring data segments. Forinstance, a multiple of the pilot patterns of the two neighbouring datasegments, between which the (common) edge pilots are provided, can beselected. If there is only a single neighbouring data segment (if theedge pilots are provided at the beginning or end (in frequencydirection) of a frame), the pilot pattern is fitted to the pilot patternof the single neighbouring data segment. In other words, the single edgepilots, that are common to the one or more neighbouring data segments,must be compatible and fit with the pilot patterns of these one or moreneighbouring data segments.

FIG. 16 shows a schematic block diagram of a broadcast system accordingto the present invention. In this embodiment, a transmitter (Tx) 30 asschematically depicted in FIG. 2 and a plurality of various receivers(Rx) 100, 120 are provided for receiving data broadcast by saidtransmitter 30. The receivers 100 may, for instance, be stationaryreceivers, e.g. in accordance with the DVB-T2 standard, and thereceivers 120 may, for instance, be mobile receivers, e.g. in accordancewith the upcoming DVB-NGH standard. The transmission signals of thetransmitter 30 are constructed as explained above, i.e. may have asuperframe structure as depicted in FIG. 9, and are not particularlyadapted only for reception by a single type of receivers, but by bothtypes of receivers 100, 120.

An embodiment of a (stationary) receiver 100 is schematically depictedin FIG. 17. It comprises a receiving unit 102 for receiving a demappinginput data stream Q′, which basically corresponds to the mapping outputdata stream Q transmitted by the transmitter 30, but possibly disturbeddue to disturbances introduced by the transmission channel between thetransmitter 30 and the receiver 100. The received demapping input datastream Q′ is provided to a demapping apparatus 104 which then demaps thedesired data stream (i.e. the desired service) Sx′ therefrom. Saiddemapping will be explained in more detail below. Thereafter, thedemapped data stream Sx′ is further processed in a post-processing unit106. Said post-processing may include cell/time deinterleaving,constellation demapping, bit deinterleaving, LDPC/BCH decoding, BBFRAMEprocessing, dejittering and null packet reinserting as, for instance,commonly provided in a receiver according to the DVB-T2 standard. Aftersaid post-processing, the desired data stream Ix′, which corresponds toone of the transmitter input data streams I1, I2, . . . , Im, isoutputted.

An embodiment of the demapping apparatus 104 is schematically depictedin FIG. 18. Said demapping apparatus 104 comprises a data input 110, atwhich the demapping input data stream Q′ is received. Said demappinginput data stream Q′ is constructed as explained above for the mappingoutput data stream Q. It comprises one or more first frames F1 and oneor more second frames F2, which are alternately arranged. The framestructures of the first frames F1 and the second frames F2 are generallydifferent, and for each frame structure various embodiments exist, asexplained above in detail.

The received demapping input data stream Q′ is then provided to a streamdemapping unit 112, in which the first frames F1 are demapped from thedemapping input data stream Q′. These first frames F1 are then providedto a frame demapping unit 114, in which they are further demapped forobtaining a desired mapping output data stream Sx′, which is thenoutputted by the data output 116 for post-processing by thepost-processing unit 106.

The stream demapping and frame demapping performed in this embodiment ofthe demapping apparatus 104 is commonly known and, for instance, beperformed in accordance with the DVB-T2 standard, if the demapppingapparatus 104 is part of a stationary receiver 100 in accordance withthe DVB-T2 standard, as is the case in this embodiment. Hence, nofurther details need to be explained here, as all these details aregenerally known in the art. The F1 frames may, for instance, be the T2frames of a superframe structure shown in FIG. 9, having a framestructure as, for instance, shown in FIGS. 3 and 4. Of course, however,other frame structures and other stream structures may be used as well,in which case the demapping apparatus 104 and its elements are adaptedaccordingly.

An embodiment of a receiver 120 in accordance with the present inventionis schematically depicted in FIG. 19. The general layout of the receiver120 is, to some extent, similar (or even the same) as the layout of thereceiver 100 as depicted in FIG. 17. However, the layout and function ofthe separate units of the receivers 100, 120 are different.

In an example at two reception antennas 121 a, 121 b and two receivingunits 122 a, 122 b (the reception antennas may also be part of thereceiving units 122) the receiver input data stream Qa′, Qb′ arereceived. These are provided to a demapping apparatus 124, whichincludes MIMO mode detection units 123 a, 123 b, which detect the MIMOmode applied to the data blocks of the mapping input data streams and/orthe data segments in the transmitter, e.g. by evaluating the respectivesignalling information indicating said MIMO mode and/or by evaluatingthe received signals (e.g. by detection of the respective pilotpattern). Depending thereon, a corresponding processing is performed.For instance, if to the service that shall be received by the receiver,a MIMO mode is applied, the corresponding MIMO decoding (e.g. anAlamouti decoding) is applied that corresponds to the encoding performedin the encoder.

Further, in an embodiment it is possible, in particular for a MIMOreceiver, to switch off one or more reception paths (e.g. by a controlunit 125 via a feedback from the MIMO mode detection units 123 a, 123 bto the respective reception antenna 121 a, 121 b and/or the respectivereceiving unit 122 a, 122 b), e.g. if SISO or MISO scheme is applied tothe desired service, since then over all transmission pathssubstantially identical data are transmitted. In this way power can besaved. Still further, in an embodiment the data received over thedifferent reception paths may be combined to improve the quality of thereceived data.

In other broadcast systems, e.g. according to DVB-T2, the complete frameis either transmitted in SISO scheme or in MISO scheme. In the lattercase the receiver must always equalize spatially. If also MIMO scheme isavailable so that per frame MIMO scheme is selected or not, the receivermust always have multiple reception antennas and apply spatialequalization. According to the present invention, however, differentclasses of receivers can be used in the same broadcast system and by useof the same broadcast signals. In particular, receivers that can receiveMIMO signals, but also receivers that can at least receive MEMO or SISOsignals can be used according to the present invention. Thus, thepresent invention enables also the use of a receiver having only asingle reception antenna, which may receive and decode MISO and SISOsignals, but ignores MIMO signals.

The output of the MEMO mode detection units 123 a, 123 b is provided todemapping units 124 a, 124 b, which may also be a combined demappingunit in an embodiment (e.g. if spatial equalization has to beperformed). Therein, the desired data stream is demapped (and, ifnecessary, decoded in separate or a combined decoding unit(s) 127provided in one or both of said demapping units 124 a, 124 b, orgenerally in the demapping apparatus 124), which is thereafter subjectedto post-processing in the post-processing unit 126, to obtain thedesired receiver output data stream Iy′. The post-processing in thepost-processing 126 may generally be similar or identical to thepost-processing performed in the post-processing unit 106 of thereceiver 100, however is adapted such that it interrelates with thepre-processing performed in the pre-processing unit 34 of thetransmitter 30. Hence, if the pre-processing in the pre-processing unit34 of the transmitter 30 is, for instance, performed in accordance withthe DVB-T2 or DVB-C2 standard, the post-processing in thepost-processing unit 126 is adapted accordingly in accordance with therespective standard.

Similarly, in another embodiment of the transmitter, in addition to orinstead of the MIMO mode detection units 123 a, 123 b respective pilotpattern detection units may be provided for detection of the pilotpatterns. Based on the detected pilot pattern, the receiver may decideto perform channel estimation either in time and/or frequency direction(interpolation) and decide what kind of further processing of thereceived data is required.

It shall be noted that multiple services multiplexing is also possibleaccording to the present invention, according to which different PLPsare transmitted over the different transmit antennas in case of MIMO.For example, two different PLPs might be mapped onto the differenttransmission paths of a MIMO encoded data symbols, while the receivermight e.g. process one PLP instantaneously, and store another PLP forlater use or combine both PLPs (as in case of scalable video coding).

An embodiment of one path of the demapping apparatus 124 isschematically depicted in FIG. 20. Again, the demapping apparatus 124generally comprises the same layout as the demapping apparatus 104 ofthe receiver 100. However, the layout and functions of the separateunits of the demapping apparatus 124 are different.

At the data input 130 the demapping input data stream Q′ is received,which is provided for stream demapping in a stream demapping unit 132.Here, the frames F2 are demapped from the demapping input data streamQ′. These frames F2 may, for instance, be incorporated into thesuperframe structure as provided according to the DVB-T2 standard as FEFframes as shown in FIG. 9. These frames F2 are then provided to a MIMOmode detection unit 123 a (and/or a pilot pattern detection unit) andthen to a frame demapping unit 134, which demaps a demapping output datastream Sy′ from said second frames. Said second frames F2 generally havea frame structure, which is different from the frame structure of thefirst frames F1, which second frame structure has been explained abovewith various modifications in FIGS. 7, 8, 10 to 12.

In particular, said frame demapping unit 134 is adapted for demappingsaid second frames F2 comprising a preamble portion 40 and a payloadportion 50 into said demapping output data stream Sy′. Said framedemapping unit 134 is particularly adapted for demapping the signallingdata Si from the preamble portion 40 and for demapping the data blocksof the demapping output data stream Sy′ from the payload portion 50 byuse of said signalling information Si. The derived demapping output datastream Sy′ is then provided to a data output 136 for output to thepost-processing unit 126.

Since the frame structure of the second frames F2 uses, as explainedabove, a segmented concept, according to which the payload portion issegmented into data segments, a narrow-band receiver 120 can be used,which, in some embodiments, must not be able to be tuned to and receivethe complete channel bandwidth of the complete frame F2, but must onlybe able to be tuned to and receive a bandwidth portion of said totalchannel bandwidth. This is possible, despite the frame structures ofboth the first and second frames F1, F2 use the total channel bandwidth,which, however, can slightly vary for the two types of frames (e.g. 7.61MHz for a first type, and 7.62 MHz for the second type of frames), i.e.the channel bandwidth of both types is in the same order.

The size of the bandwidth portion of the receiver 120 depends on thebandwidth portion covered by data blocks of the desired demapping outputdata stream Sy′. If, for instance, all the data blocks of the desireddemapping output data stream Sy′ are stored in a single data segmentonly, it is sufficient if the receiver can be tuned to and receive thebandwidth covered by said data segment. If, as provided in anotherembodiment, the data blocks of the desired demapping output data streamSy′ (in frequency direction) cover two or more (neighbouring or notneighbouring) data segments at a particular moment in time, the receivermust be able to be tuned to and receive a larger bandwidth portion.Further, the invention also enables the use of receivers that are ableto receive the complete channel bandwidth and not only a portionthereof, as is the case in preferred receivers of the present invention.

The information about the bandwidth portion, in particular its size andits frequencies, are generally signalled from the transmitter to thereceiver within the signalling information. This signalling informationalso contains information about the locations of the data blocks of thevarious data streams, to enable the receiver to change its tuningaccordingly. As explained above, particularly with reference to FIGS. 11to 13, for signalling of the required information, various embodimentsexist. Hence, the frame demapping unit 134 is adapted accordingly tofind, collect, deinterleave, decode and make use of said signallinginformation for demapping the desired data blocks from the frames F2.

FIG. 21 shows another embodiment of a broadcast system in accordancewith the present invention. In this embodiment, the transmitter 70 isused as depicted in FIG. 15. According to said embodiment, only a singletype of frames F is used (i.e. no superframe structure of superframes F3containing first and second frames F1, F2 is used, but anothersuperframe structure containing only frames F), onto which the datablocks of the various data streams are mapped. The mapping is providedsuch that the data blocks are spread in time and frequency over variousdata symbols and various data segments of the frames F, such as, forinstance, depicted in FIG. 10. Accordingly, only a single type ofreceivers 140 (preferably a mobile receiver) is provided in thebroadcast system, which is designed to enable reception and decoding ofdata streams transmitted by said type of transmitter 70.

The layout of such a receiver 140 is schematically shown in FIG. 22,which corresponds to the layout of the receivers 100, 120. The receiver140 also comprises a receiving unit 142, a demapping apparatus 144including a MIMO mode (and/or pilot pattern) detection unit 143, and apost-processing unit 146. However, particularly the demapping apparatus144 is different as shown in FIG. 23. In particular, said demappingapparatus 144 does not comprise any stream demapping unit as provided inthe demapping apparatus 104, 124 of the receivers 100, 120, since nosuperframe structure is used, but the demapping input data stream Q′only comprises a single type of frames. From the data input 150, saiddemapping input data stream Q′ is provided to the MIMO mode (and/orpilot pattern) detection unit 143 and then to the frame demapping unit152, by which the demapping output data stream Sy′ is demapped, which isthen outputted via the data output 154 for post-processing. The framedemapping unit 152 generally has the same layout and function as theframe demapping unit 134 of the demapping apparatus 124 of the secondtype (mobile) receiver 120, since the frame structure of the frames Fused by the transmitter 70 is generally the same as the frame structureof the second frames F2 used by the transmitter 30. Of course, the samevarious embodiments exist also for the frame mapping unit 152 that havebeen explained above for the frame demapping unit 134.

For reception of the receiver input data stream Q′, a single antenna anda single tuner is generally sufficient in the receiver. Receivers (e.g.mobile receivers) may, however, also be provided with two or moreantennas and/or two or more tuner, which can particularly be used toadvantage if the data blocks of the data stream that shall be receivedare spread (in time and/or frequency) over more than one data segmentand/or data symbol. For instance, in case of spreading in time, a firstantenna (and/or tuner) can be controlled to receive a first data blockmapped onto a first data segment and the second antenna (and/or tuner)can be controlled to “look ahead” in time (e.g. be tuned to anotherfrequency) for reception of the next data block mapped onto another datasegment at the appropriate time. In another embodiment, in particular incase of spreading in frequency, both antennas (and/or tuners) can becontrolled to receive the data blocks mapped onto the two data segmentsat the same time. In this way, tuning time in the receiver can be savedand more sleeping times for the receivers can possibly be provided.Further, in an embodiment, a receiver having two reception antennas canuse the second reception antenna to “look ahead” and receive a secondservice (that is e.g. stored in the receiver) while the first receptionantenna receives a first service, for whose reception the secondreception antenna is not needed, i.e., for SISO or MISO scheme.

Preferably, at least two reception antennas are provided in a mobilereceiver to make use of the various MIMO modes explained above. However,MIMO and MISO can also be used with transmitters and receivers havingmore than two antennas, and also Alamouti coding is just one example ofa coding scheme used in MISO. Other space/time as well asspace/frequency coding schemes can be used as well.

As explained above, it is one target of state of upcoming mobilebroadcast standards such as NGH to provide mixed MIMO (or MISO) and SISOoperation. This allows a higher level of flexibility, e.g. differentservices can be received with different robustness, decoding complexityor even receiver types (handheld, in-car, single or double receptionantenna).

MIMO or MISO transmission schemes (both schemes are sometimes commonlydenoted by the term MIXO) can be beneficial, because they exploit thespatial dimension (more robustness/higher data rates). However, SISO isstill the more proven technique and requires only one transmissionantenna. Introduction of MIXO for future broadcasting could be achievedby two approaches:

A) Introducing MIXO transmission could be done in a “hard cut” manner:change the complete network from SISO to MIMO and transmit from thereonwith several (e.g., two) transmission antennas exclusively. It is to benoted that a typical MIXO scheme for broadcasting applies dual-polarizedMIXO, i.e., one antenna element transmits with a vertically polarizedcomponent, the other element uses horizontally polarized radio waves

B) For graceful introduction of MIXO schemes, it is possible to use SISOfor some time, then change to MIXO, back to SISO and so on. In DVB-T2,the standard even allows to subsequently transmit a T2 Frame in SISOoperation, while the next T2 Frame could use MISO.

Changing from MIXO to SISO transmission induces that during SISOtransmission the second transmission antenna is switched off. This ishowever hardly possible, if the transmit towers radiate largetransmission powers (as is typically done in terrestrial broadcasting).

Thus, having pure MIXO and SISO in subsequent (and rather short) timeintervals is impossible, if the transmit antennas require a constanttransmit power.

As explained above in segmented OFDM it is possible to use certain datasegments (data slices) for SISO transmission, while others are used forMIXO providing in particular the advantage of reduced pilot overhead forchannel estimation. Receivers for MIXO generally estimate twice thenumber of channels as two transmit antennas are used.

The general separation in frequency direction is depicted in FIG. 26Cindicating the doubled amount of MIXO pilots. In principal, each segmentmight carry a different scheme (SISO, MISO or MIMO), e.g. five datasegments carrying the schemes: SISO-MIXO-SISO-MIXO-MIXO.

Assuming in an example that a first transmission antenna transmits dataduring SISO operation (e.g., the vertically polarized antenna), for MIXOfurther transmission antennas are used. In this example, only onefurther transmission antenna (i.e. a second antenna), which e.g. mightbe the horizontally polarized transmission antenna, is provided. Thus,in this example, all subcarriers of the segmented OFDM use the verticalcomponent, while the subcarriers used in the MIXO segments further usethe horizontal subcarriers (at the corresponding frequencies), as can beseen in FIG. 27.

While the vertically polarized OFDM signal can be generated by a normalOFDM modulation, the horizontal signal can be generated with twoapproaches.

In a first approach all subcarriers are set to zero, where no horizontalcomponent is to be transmitted (i.e. in the SISO segments). Then, OFDMcoding is performed using the complete bandwidth (of all data segments,including the SISO segments with the inserted zeros in frequencydomain), i.e. single OFDM symbols are formed for the horizontallypolarized subcarriers.

In a second approach a narrowband OFDM coding is performed for each MIXOdata segment in the equivalent complex baseband and the individualsignals are mixed to the center frequencies of each corresponding datasegment. In the example, two OFDM signals are generated, one with ⅕ andanother one with ⅖ of the complete bandwidth. The first one OFDM signalis shifted to the second data segment, the other OFDM signal is shiftedto the last two data segments. However, frequency and timesynchronization generally need to be rather accurate.

Both approaches generally yield the same result, which can beinterpreted as using zero-padding for SISO subcarriers, i.e. thosesubcarriers which are not transmitted over a particular transmissionantenna.

A further possible solution would be that the horizontal subcarriers inthe SISO data segments are not filled with zeros, but rather arereplaced by the same symbols as used in the SISO part, which aretransmitted over the vertical antenna. However, typically, there is arather large cross-polar discrimination (XPD, about 10 dB), which meansthat the horizontally SISO segments are received by a pure SISO receiverwith smaller power (up to 3 dB loss, if two antennas are used in theMIMO or MISO scheme).

As typically both transmission antennas should radiate the same power,the subcarriers of the MIXO data segments are preferably be boosted byan appropriate scaling factor (indicated by larger arrays in FIG. 27).As discussed above, each component may use half of the overalltransmission power. Since the horizontally polarized subcarriers occurin only ⅗ of the complete bandwidth, the power of these subcarriers canbe boosted by a factor of 5/3 compared to the subcarriers of thevertical component (which occur in the complete bandwidth). In summary,this approach splits the overall transmit power (that would be used forSISO-only transmission) into two equal parts. However, the second (MIXO)part is distributed over just some of the data segments, while on otherdata segments no power is radiated. Thus, the power of the MIXO datasegments is boosted. More precisely, the power inside the MIXO datasegments of the additional antennas, which are used for MIXO, is boostedcompared to the power of the antenna, which is used for both SISO andMIXO.

However, there could be practical problems, as the receiver wouldtypically detect the power imbalances between the different transmittedsignals. For most MIXO schemes, this impedes decoding. Thus, powerimbalances between the transmitter components should preferably beavoided in some cases. The following approach enables this.

For the following example the overall transmission power (which would beused for SISO-only transmission and which would be transmitted over allN_seg segments) is denoted as P_SISO, the number of MIXO data segmentsis denoted by N_MIXO and the number of transmission antennas used forMIXO is denoted by N_ant. Then all subcarriers of both transmissionantennas are downscaled (compared to the SISO-only case) by a factorsuch that the overall radiated power is still P_SISO.

More precisely, the downscaling of the power for all subcarriers is, forinstance, computed by the factor D=P_SISO/(N_seg−N_MIXO+N_ant*N_MIXO).The downscaling of the magnitudes of all subcarriers is doneappropriately with √D).

FIG. 28 depicts the scenario: the transmission antennas radiate ingeneral different powers in total; however, the sum of those powersequals P_SISO. Further, it is ensured that all subcarriers use the sametransmission power such that there is no power imbalance.

The second antenna (horizontal) in this example could in addition beused to further reduce the peak-to-average power ratio (PAPR—typicalproblem for OFDM). Moreover, in an embodiment some non-zero symbols areinserted, e.g. tone reservation carriers at the positions of the pilots.Newly inserted pilots however still need to be orthogonal to theoriginal SISO pilots, i.e. all related channel estimationfunctionalities need to be maintained. Preferably, the boosting factorexplained above should then be reduced accordingly. Thus, these newlyinserted pilots do not disturb the original pilots, if the receivertreats them as MIXO pilots, thereby eliminating the new pilots. Thiscould be exploited to further reduce the PARP by selecting the pilotsappropriately. For instance, in a brute force approach all permutationsare tried and the one is selected, which minimizes the PAPR.

As mentioned above, the further transmission antennas use differentlypolarized subcarriers than the first antenna. For instance, in anembodiment of a transmission apparatus 30′ as depicted in FIG. 29A afirst transmission antenna 30 a uses vertically polarized subcarriers,while a second transmission antenna 30 b (and still further transmissionantennas, if available and used) uses horizontally polarizedsubcarriers. Alternatively, the various antennas may use differentcircular polarizations. In still another alternative embodiment of atransmission apparatus 30″ as shown in FIG. 29B the various transmissionantennas 30 c, 30 d may be located at considerable distances from eachother, i.e. not at substantially the same place, and use the samepolarization.

Next, a further embodiment of a transmission apparatus for use invarious broadcast systems is described.

Generally, SISO transmissions use only one transmission antenna, whileMIXO transmissions take advantage of several transmission antennas(wherein two transmission antennas is the most likely case in theupcoming DVB-NGH systems).

If MIMO and SISO services are mixed in time, e.g. partitioned by thehelp of frames, it occurs that one transmission antenna operatesconstantly, while the second (and further) transmission antenna onlytransmits during the MIXO transmission periods as schematically shown inFIG. 30A for mixed MIMO/SISO operation.

In order to achieve the same overall transmission power level on thechannel the SISO power level of the single transmission antennagenerally should be 3 dB higher compared to the power level on each ofthe two MIXO transmission antennas, i.e. during MIXO operation the samepower has to be radiated as in SISO operation, thus splitting the poweronto two transmission antennas (3 dB loss).

Having different power levels on different transmission antennas isgenerally no problem for transmission systems with limited transmissionpower levels (WLAN, WIMAX, LTE, . . . ). These systems can easily switchbetween different MIMO and SISO schemes. This is different for largescale transmission systems, e.g. nationwide terrestrial broadcastsystems such as DVB-T2 or the upcoming NGH standard systems. Thetransmission apparatus of these broadcast networks typically covers verylarge areas, therefore the transmission power level needs to very high.It is quite difficult to switch on and off frequently blocks of a highpower level signal chain, which would be needed on the secondtransmission path of the NGH MIMO scheme (during SISO transmissionperiods).

It is therefore proposed to allocate the power level in a way that it iskept constant over the different transmission periods (i.e. SISO andMIXO frames). This means that the SISO transmission power (being so farfed to a single transmit antenna) is split up to the two (or more)transmission paths. Logically the two transmission paths build thereforea kind of SFN (Single Frequency Network).

FIG. 30B shows the now constant power allocation across the differentMIMO and SISO operation periods. Each transmission antenna radiates thesame power. Preferably, the additional MIXO antennas (here only thesecond antenna) duplicate the data from the original SISO antenna, i.e.,during the SISO frames, both transmission antennas transmit the samedata.

For fixed reception conditions (i.e. where the polarization of thereception is aligned to the transmission polarization) the receivedsignal strength might be decreased by 3 dB. On the other hand, portableand mobile receivers gain from the increased polarization diversity, asdifferent reception angles can always deploy the overlaid (or combined)reception field strengths of both transmission polarizations. Mobilereceivers will in average have therefore better reception conditions.This is even more true if reception diversity with different receiverpaths (e.g. orthogonal reception antennas) is applied.

In summary, the present invention enables the use of narrow-bandreceivers having a low power consumption even if the frame structureused by the transmitter of the multi-carrier broadcast system has a muchbroader channel bandwidth. Further, various embodiments are provided,which enable further savings in power consumption of receivers, which isparticularly important for mobile receivers. Still further, an increasedor at least selectable robustness for selected services due to the useof time and/or frequency diversity in the mapping of data blocks of theservices onto frames having a segmented frame structure can be achieved.

A data segment of the payload portion can be used only for a single datastream or can be split up in time and/or frequency direction for use bydata blocks of two or more data streams. The respective use of the datasegment, i.e. the mapping of the data blocks of the various data streamson the data segments of the frames, can be static (i.e. continuouslyfixed) for the whole transmission of a data stream, can be quasi-static(i.e. fixed for a group of frames or only a single frame, i.e. can bechanged from frame to frame) or can be continuously changed (i.e. alsowith frames). In the latter embodiments more signalling is requiredcompared to the first (static) embodiment.

Further, according to the present invention various levels of robustnessand various data rates can be selected by the transmitter and can bereceived by the receiver through the ability to select the MIMO modeand/or the pilot pattern per PLP and/or per data slice. For instance, alow resolution data stream can be transmitted using SISO or MISO and acorresponding high resolution data stream can be transmitted in MIMO.

The invention also enables the application of scalable video coding,according to which the same data are transmitted as a high resolutiondata stream (with lower robustness) and as a low resolution data stream(with higher robustness). If the receiver is, e.g. due to bad receptionconditions, not able to receive the high resolution data stream it canswitch to the corresponding (“associated”) low resolution data stream.

The invention has been illustrated and described in detail in thedrawings and foregoing description, but such illustration anddescription are to be considered illustrative or exemplary and notrestrictive. The invention is not limited to the disclosed embodiments.Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single element or other unit may fulfil the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicatethat a combination of these measures cannot be used to advantage.

A computer program may be stored/distributed on a suitable medium, suchas an optical storage medium or a solid-state medium supplied togetherwith or as part of other hardware, but may also be distributed in otherforms, such as via the Internet or other wired or wirelesstelecommunication systems.

Any reference signs in the claims should not be construed as limitingthe scope.

In an embodiment of the receiver said MIMO mode detection means isadapted for detecting one of a SISO scheme, MISO scheme or MIMO scheme.

In an embodiment of the receiver said MIMO mode detection means isadapted for detecting the MIMO mode from frame to frame or from a groupof frames to a next group of frames.

In an embodiment of the receiver said MIMO mode detection means isadapted for detecting the MIMO mode from data symbol to data symbol orfrom a group of data symbols to a next group of data symbols.

In an embodiment of the receiver said pilot pattern detection means isadapted for detecting edge pilots between neighboring data segments,said edge pilots fitting with the pilot patterns of both neighboringdata segments.

In an embodiment of the receiver said pilot pattern detection means isadapted for detecting the pilot pattern from frame to frame or from agroup of frames to a next group of frames.

In an embodiment of the receiver said pilot pattern detection means isadapted for detecting the pilot pattern from data symbol to data symbolor from a group of data symbols to a next group of data symbols.

In an embodiment of the receiver said MIMO mode detection means and/orsaid pilot pattern detection means is adapted for demapping signallinginformation from said frame, said signalling information including MIMOmode information indicating the selected MIMO mode of the data blocksper data segment and/or per mapping input data stream and/or pilotpattern information indicating the selected pilot pattern per datasegment and/or per mapping input data stream.

In an embodiment of the receiver said frame demapping means is adaptedfor demapping said signalling information from one or more preamblesignalling blocks mapped onto preamble symbols of a preamble portion ofsaid frames, from one or more payload portion signalling blocks mappedonto data symbols of said payload portion or in-band from one or moredata blocks mapped onto data symbols of said payload portion.

In an embodiment of the receiver it comprises one or more demappingunits per reception path of a receiver, into which said apparatus isincluded, wherein said one or more demapping units are adapted forindividually demapping the data blocks from the provided demapping inputdata stream.

In an embodiment of the receiver at least one demapping unit comprisesdecoding means for decoding the data blocks provided to said at leastone demapping unit.

In an embodiment of the receiver said frame demapping means is adaptedfor demapping the data blocks of a demapping output data stream fromvarious data symbols and various data segments of said frame, over whichsaid data blocks are spread in time and frequency.

In an embodiment of the receiver said receiving unit comprises at leasttwo receiving sub-units for receiving different demapping input datastreams, and said receiver apparatus further comprises a control unitfor switching off at least one receiving sub-units or for combining thereception signal received by said receiving sub-unit, if the MIMO modedetection unit has detected that the demapping input data streamcurrently received uses SISO scheme or MISO scheme.

1. (canceled)
 2. A transmission apparatus comprising: circuitryconfigured to map multiple input data streams representing physical datapipes (PLPs) onto a transmission frame, the transmission frame having achannel bandwidth and including OFDM symbols following each other in atime direction and being arranged into groups of OFDM symbols, eachgroup of OFDM symbols being assigned a MIMO mode, the MIMO modes beingselected from a SISO scheme, a MISO scheme and a MIMO scheme, wherein afirst group of OFDM symbols in the frame is assigned a different MIMOmode from a second group of OFDM symbols in the frame; and outputcircuitry configured to convey output data streams including one or moreframes including the transmission frame to transmission circuitry. 3.The transmission apparatus according to claim 2, wherein a group of OFDMsymbols is segmented into slices, and the circuitry is configured to mapa single PLP to a slice.
 4. The transmission apparatus according toclaim 2, wherein the circuitry is configured to assign a different MIMOmode from one group of OFDM symbols to a next group of OFDM symbols inthe time direction.
 5. The transmission apparatus according to claim 4,wherein one group of OFDM symbols of the groups of OFDM symbols issegmented into slices.
 6. The transmission apparatus according to claim2, wherein each of the groups of OFDM symbols is a payload data portion.7. The transmission apparatus according to claim 6, wherein a payloaddata portion includes a payload portion signaling block includingdetailed signaling information.
 8. The transmission apparatus accordingto claim 7, wherein the detailed signaling information includes the MIMOmode.
 9. The transmission apparatus according to claim 6, wherein thecircuitry is configured to map a preamble to the frame, the preambleincluding high level signaling.
 10. The transmission apparatus accordingto claim 2, further comprising pilot insertion circuitry configured toinsert pilots according to different pilot patterns for the MIMO modeassigned to a group of OFDM symbols.
 11. A method of transmitting datacomprising: mapping, by circuitry, multiple input data streamsrepresenting physical data pipes (PLPs) onto a transmission frame, thetransmission frame having a channel bandwidth and including OFDM symbolsfollowing each other in a time direction and being arranged into groupsof OFDM symbols, each group of OFDM symbols being assigned MIMO a mode,the MIMO modes being selected from a SISO scheme, a MISO scheme and aMIMO scheme, wherein a first group of OFDM symbols in the frame isassigned a different MIMO mode from a second group of OFDM symbols inthe frame; and conveying an output data stream comprising one or moreframes including the transmission frame to transmission circuitry.
 12. Areceiver apparatus comprising: receiver circuitry configured to receiveinput data streams having a transmission frame structure andrepresenting physical data pipes (PLPs); demapping circuitry configuredto demap the input data streams from a transmission frame, thetransmission frame having a channel bandwidth and including OFDM symbolsfollowing each other in a time direction and being arranged into groupsof OFDM symbols, each group of OFDM symbols having associated thereto anindication of a MIMO mode, the MIMO modes being selected from a SISOscheme, a MISO scheme and a MIMO scheme, wherein a first group of OFDMsymbols in the frame has associated thereto a different MIMO mode from asecond group of OFDM symbols in the frame; and output circuitryconfigured to convey output data streams demapped from one or moreframes including the transmission frame to post processing circuitry.13. The receiver apparatus according to claim 12, wherein a group ofOFDM symbols is segmented into slices, and the circuitry is configuredto demap a single PLP from a slice.
 14. The receiver apparatus accordingto claim 12, wherein the circuitry is configured to derive a differentMIMO mode from one group of OFDM symbols to a next group of OFDM symbolsin the time direction.
 15. The receiver apparatus according to claim 14,wherein one group of OFDM symbols of the groups of OFDM symbols issegmented into slices.
 16. The receiver apparatus according to claim 12,wherein each of the groups of OFDM symbols is a payload data portion.17. The receiver apparatus according to claim 16, wherein a payload dataportion includes a payload portion signaling block including detailedsignaling information.
 18. The receiver apparatus according to claim 17,wherein the detailed signaling information includes the MIMO mode. 19.The receiver apparatus according to claim 16, wherein the demappingcircuitry is configured to demap a preamble to the frame, the preambleincluding high level signaling.
 20. The receiver apparatus according toclaim 12, further comprising pilot detection circuitry configured todetect pilots, the pilots having different pilot patterns for the MIMOmode associated with a group of OFDM symbols.
 21. A method of receivingdata comprising: receiving, by circuitry, input data streams having atransmission frame structure and representing physical data pipes(PLPs); demapping the input data streams from the transmission frame,the transmission frame having a channel bandwidth and including OFDMsymbols following each other in a time direction and being arranged intogroups of OFDM symbols, each group of OFDM symbols having associatedthereto an indication of a MIMO mode, the MIMO modes being selected froma SISO scheme, a MISO scheme and a MIMO scheme, wherein a first group ofOFDM symbols in the frame has associated thereto a different MIMO modefrom a second group of OFDM symbols in the frame; and conveying outputdata streams demapped from one or more frames including the transmissionframe to post processing circuitry.